Files : API changes for 5.5 - Update file API changes to support the add/remove(update) of tags from file

Changes to support the update of tags from a file.

Need to update the Update file API for add/delete(update) the tags from file
A user can get the list of tags already added into the file from Get file info API.
1.Below Format will be added into the Update file request xml in order to add or update tags
<tags>
   <tag>twitter</tag>
   <tag>facebook</tag>
   <tag>snapchat</tag>
</tags>
2. To delete all tags from a file use empty <tags/> or <tags></tags> format.
3. If there are no <tags> tag is provided then you do not need to update the tags in file.

NOTE: Tag should be updated in api version 12.