Custom uploadFile option. Closes #117

With this option, in assetManager, is possible to override the built-in
method

src/asset_manager/config/config.js

@@ -13,4 +13,12 @@ module.exports =  {
 
   // Label for the add button
   addBtnText: 'Add image',
+
+  // Custom uploadFile function
+  // @example
+  // uploadFile: function(e) {
+  //   var files = e.dataTransfer ? e.dataTransfer.files : e.target.files;
+  //   // ...send somewhere
+  // }
+  uploadFile: '',
 };

src/asset_manager/view/FileUploader.js

@@ -21,6 +21,12 @@ module.exports = Backbone.View.extend({
     this.uploadId  = this.pfx + 'uploadFile';
     this.disabled  = !this.config.upload;
     this.events['change #' + this.uploadId]  = 'uploadFile';
+    let uploadFile = this.config.uploadFile;
+
+    if (uploadFile) {
+      this.uploadFile = uploadFile.bind(this);
+    }
+
     this.delegateEvents();
   },