Added SVN add/delete/revert directory.

Summary:
Added "SVN Add" on directory addition with appropriate "SVN Revert" action.
Also for directories already under VCS control added "SVN Delete" action.

Test Plan:
1. Create empty directory.
2. Try "SVN Add" on it: it should be added.
3. Try "SVN Revert" on it: it should be reverted.
4. Try "SVN Add", then "SVN Commit". It should be commited fine.
5. Try "SVN Delete", then "SVN Commit". It should be deleted from CVS and commited fine.
6. Try the same with a dir with an empty file in it right-clicking on the directory name and inside directory.

Reviewers: meven, elvisangelaccio

Reviewed By: meven

Differential Revision: https://phabricator.kde.org/D27652