Extract common code for Angular and Backbone

[bgaillard]

For now we have 2 separate request managers for Angular and Backbone. The Backbone implementation overwrites Backbone methods and uses jQuery, the Angular implementation overwrites the XMLHttpRequest objecft principally and uses function and object utilities embedded in the OAuth.JS library.

Update the code of request manager with the following modifications :

• Remove the use of jQuery mobile in the Backbone request manager
• Extract all the code which is common to Angular and Backbone to the AbstractRequestManager class
• Test the refactored Angular request manager
• Test the refactored Backbone request manager