Search on collection drawer implemented, & resolved minor bugs

**Feature Enhancement**

* Bug resolved in search on collection drawer. 
    * Type 3 or more than 3 characters and press enter , it will search the appropriate elements and results will be displayed on left drawer

* get_node_metadata() --> ```methods.py``` modified
    * unused parameter ```node_type``` removed.

* For saving metadata of any node requires a node first, and on the basis of that node its metadata attributes are filled . Hence ```get_node_metadata()``` function is called after page, file & topic node gets saved.

* Now metadata wil be edited only on click of metadata tab from topic context, previously it was calling function ```get_node_metadata``` without editing any of the metadata fields all the time when topic node was getting saved.

* Minor changes in ```search_drawer``` --> ajax_views.py 
    * Modified the search querries. Condition added to search in collection drawers only from page, file and quiz objects since these are resources.

* Bug resolved in creating new page. 
   * Since initially it was trying to save metadata info without any page node context while creating page. Hence removed the code for saving metadata info from ```get_node_common_fields()```  --> methods,py and its kept after the page node gets saved. 

* Bug resolved while editing page node.
    * Commented ```check_existence_textObj_mobwrite``` tag from ```add_editor.html``` .

* Image thumbnail url changed in ```uDashboard.html``` and ```base.html``` for displaying profile pic as a thumbnail image.
    * used ```getFileThumbnail``` url for displaying image thumbnail. Since will use this method at every place wherever thumbnail image requires, because will be making this function generic function for creating file thumbnails, and will remove the ```getImageThumbnail``` after some period of time.

**What is to test**
* click on create new page button and check if its giving any error.

* click on edit page and, check if its giving any error.

* click on collection tab , select a collection type and search an element  from search bar on collection drawer
    * Type atleast 3 characters of desired word and press **Enter** . 
    * Few enhancement in this will be reflected in next commit, such as 
         * After searching element the previous list should populate again on erasing all text in search bar.
         * Pagination on search results.