CLI support

HaveClip listens on a local socket to which CLI process connects
and sends a command.
CLI command sync
CLI: add forgotten base command class
Configurable clipboard tracking

When tracking is disabled, HaveClip does not notice clipboard changes
automatically anymore. It will do so only when on-demand synchronization
is triggered.
Merge branch 'devel' of git.havefun.cz:haveclip-core into devel

Conflicts:
	src/ClipboardManager.cpp
Control socket: place to data storage location