Fix move and copy operations

Owing to the loss of filename, the copy operation was disabled a long time ago in (https://bugzilla.gnome.org/show_bug.cgi?id=755701). Normally, for POSIX based systems, copying /file1 to directory /folder1 is done by doing copy ('/file1', '/folder1/file1'). Since, google drive backend uses IDs as filenames (which are not human readable), so doing a copy operation normally should constitute of doing copy ('/id1', '/folder1/id2'), but instead GIO being POSIX compliant does copy ('/id1', '/folder/id1').

Furthermore, after the copy operation has been done, nautilus performs a query_info operation on the path /folder1/id1 (to check if the file has actually been copied) but since the newly created file inside /folder1 has the new path /folder1/id2 (where 'id2' is generated by Drive API) this operation fails resulting in an error and the new file's title being set to id1 (Loss of titles).

To counter this issue, we store id1 in Properties Resource on the new file being created, and insert a "fake" entry into the cache. This fake entry (('id1', 'parent') -> GDataEntry) gives the illusion that the file exists after the copy operation, and hence the query_info operation doesn't fail, and copies the file (while retaining title) successfully.

This commit enables copy operation and handles most of the quirky cases of Drive, e.g. files having same title in a directory, file being copied over to same folder, etc.

Depends upon: libgdata!7 (merged) Fixes: #8 (closed)