Reimplement X11Watcher

[ErikBjare]

A reimplementation of the X11Watcher using xprop instead of the old Xlib wrapper library is needed. This was called for due to some issues with the current implementaion (see issue #22).

Rescuetime uses the xprop approach and it seems easier quite frankly.

This issue makes #22 irrelevant.

Feature list:

• [ ] Log all open windows and their titles, allowing for watching of windows not in focus (for example gathering which song is played in Spotify etc.)
• [ ] Collect WM_COMMAND, _NET_WM_NAME/WM_NAME and other attributes