Added VCS plugins signals connections for outOfVersionControl() actions.

Summary:
Plugins can now do out of version control actions (D29041), so we need them to inform of their state.
This change connects every plugin signal to Dolphin on plugin instantiation.

Test Plan:
1. Try SVN Update of inaccessible repository: see SVN error message shows up.
2. Try pull inaccessible git repository: see GIT error message shows up.
3. Try SVN Commit: see SVN message.

Reviewers: #dolphin, meven, elvisangelaccio

Reviewed By: #dolphin, meven

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D29488