Make FileWatcher into a virtual class.

And create a Qt and an inotify implementation.
Add new CMakeLists for integrating Google Tests.

Also add a test for the FileWatcher and WatchTower.
Add tests for WatchTower and remove a nasty race in both test and code.
WatchTower: add notification for moved/renamed files.
WatchTower: Adds test for symlink behaviour.
Starts refactoring WatchTower to be multi-platform.
Implements a native Windows version of WatchTower.
Add the WinNotificationInfo class for Windows' WatchTower.
Add informations about tests in README.
Improve implementation of WinWatchTower and integrates it.
Make inotify able to treat multiple events.
Add the config.h.in (only used for tests for now).
Refactor WatchTower to be concrete and uses a virtual Driver.
Refactor WatchTower to use a parameterised Driver.
Make the WatchTower parametric (only works for inotify).
Minor fixes to allow building on gcc < 4.7.
Add a way to interrupt the WatchTower.
Integrate Windows implementation in templated WatchTower.
Add a temporary config.h to build with qmake.

Will be removed when we switch to cmake.
Cleanup directories when they are not watched.