Launch a json list of programs at startup.

In the file startup.json you can list programs that
should start when the window manager is booted.
Load root window size from struct.

The root window size is not hardcoded to 800x600
anymore.
Load shortkeys from file and use them.

A json file defines the available shortkeys in
a bit of arcane format but for now it's still
better than having it hardcoded.
Match event types on name instead of number.

This makes the code a bit more readable and if it's
a significant performance issue we'll change it back
later.