Dataset collections - "reduce" with existing tools.

Allow users to select dataset collections in place of individual datasets for data tool parameters with multiple="true" enabled (if all elements of collection would be valid as input to this parameter).

Restrict collection reductions to flat collections. If a user wanted to reduce a nested collection they probably want to map of the subcollections reducing each and building a collection of the reductions. TODO: The sentence is probably unintelligiable, need to provide a concrete example.

A functional test demonstrating these reductions in included.

static/scripts/galaxy.tools.js

@@ -39,6 +39,11 @@ define([ "libs/underscore", "mvc/tools" ], function( _, Tools ) {
             'icon_class': 'fa-list-alt',
             'select_by': 'Run tool over multiple datasets',
             'allow_remap': true
+        },
+        'multiselect_collection': {
+            'icon_class': 'fa-folder-o',
+            'select_by': 'Run tool over dataset collection',
+            'allow_remap': false,
         }
     };