/**
 * @class Ext.exporter.Base
 * @extend Ext.Base
 * @alias exporter.base
 *
 * This is the base class for an exporter. This class is supposed to be extended to allow
 * data export to various formats.
 *
 * The purpose is to have more exporters that can take the same {@link #data data set} and export it to different
 * formats.
 *
 * Exporters are used by {@link Ext.grid.plugin.Exporter} and {@link Ext.pivot.plugin.Exporter}
 * but could also be used individually when needed.
 *
 * If there is a requirement that the above plugins should export the data to a document format
 * that is currently not supported by the `exporter` package then it's better to extend this class
 * to create a custom exporter that does that. This way both plugins can use the same custom exporter.
 *
 * There are cases when tabular data that doesn't come from a grid panel or a pivot grid needs to
 * be exported to a file. This could be achieved using the available exporters independently.
 *
 *      var exporter = Ext.Factory.exporter({
 *          type: 'excel',
 *          data: {
 *              columns: [{
 *                  text: 'Vacation',
 *                  columns: [
 *                      { text: 'Month', width: 200, style: { alignment: { horizontal: 'Right' } } },
 *                      { text: 'Days', style: { format: 'General Number' } }
 *                  ]
 *              }],
 *              groups: [{
 *                  text: 'Employees',
 *                  groups: [{
 *                      text: 'Adrian',
 *                      rows: [{
 *                          cells: [
 *                              { value: 'January' },
 *                              { value: 2 }
 *                          ]
 *                      },{
 *                          cells: [
 *                              { value: 'July' },
 *                              { value: 10 }
 *                          ]
 *                      }],
 *                      summaries: [{
 *                          cells: [
 *                              { value: 'Total' },
 *                              { value: 12 }
 *                          ]
 *                      }]
 *                  },{
 *                      text: 'John',
 *                      rows: [{
 *                          cells: [
 *                              { value: 'March' },
 *                              { value: 4 }
 *                          ]
 *                      },{
 *                          cells: [
 *                              { value: 'May' },
 *                              { value: 4 }
 *                          ]
 *                      },{
 *                          cells: [
 *                              { value: 'July' },
 *                              { value: 2 }
 *                          ]
 *                      }],
 *                      summaries: [{
 *                          cells: [
 *                              { value: 'Total' },
 *                              { value: 10 }
 *                          ]
 *                      }]
 *                  }],
 *                  summaries: [{
 *                      cells: [
 *                          { value: 'Grand total' },
 *                          { value: 22 }
 *                      ]
 *                  }]
 *              }]
 *          }
 *      });
 *
 *      // save the file
 *      exporter.saveAs().then( function() { exporter.destroy(); } );
 *
 */
 
/**
 * @cfg {Ext.exporter.data.Table} [data=null] (required)
 *
 * Data to be consumed by the exporter.
 * @accessor
 */
 
/**
 * @cfg {Boolean} [showSummary=true]
 *
 * Should group summaries be shown? The data this exporter can consume
 * may contain group summaries.
 * @accessor
 */
 
/**
 * @cfg {String} [title=null]
 *
 * Title displayed above the table. Hidden when empty
 * @accessor
 */
 
/**
 * @cfg {String} [author="Sencha"]
 *
 * The author that generated the file.
 * @accessor
 */
 
/**
 * @cfg {String} [fileName="export.txt"]
 *
 * Name of the saved file
 * @accessor
 */
 
/**
 * @cfg {String} [charset="UTF-8"]
 *
 * File's charset
 * @accessor
 */
 
/**
 * @cfg {String} [mimeType="text/plain"]
 *
 * File's mime type
 * @accessor
 */
 
/**
 * @cfg {String} [binary=false]
 *
 * Set to `true` if the exporter generates a binary file.
 * @accessor
 */
 
/**
 * @method getContent
 * Generates the file content.
 */
 
/**
 * @method saveAs
 * Save the file on user's machine using the content generated by this exporter.
 * @return {Ext.promise.Promise}
 */
 
/**
 * @method getColumnCount
 * Returns the number of columns available in the provided `columns` array.
 * It will parse the whole tree structure to count the bottom level columns too.
 * @param columns
 * @return {Number}
 */