Add Topic support

[spoorun]

Currently Topics can be added from the stream to files.

However, when using the Files module itself, a user cannot view, add, delete, edit, or search Topics, nor add them when creating or uploading a file.

[luke-]

@yurabakhtin The "Topic" field in the 'Edit' dialog of a file (right click / context menu) would be cool.

[yurabakhtin]

@luke- PR #124:

[spoorun]

Great

Will this mean that a topic can be added during the process uploading or creating a file?

Will topics be viewable/sortable when viewing file list on the files module?

[luke-]

@yurabakhtin Please see my review. I can reproduce the test error on my machine.
@spoorun No, as in other modules, the topics will only be available via the stream for the moment.

[yurabakhtin]

@luke-

Please see my review. I can reproduce the test error on my machine.

Thanks for the comment, it helped. Fixed in PR #124.

[spoorun]

See #129