Removed the prefix of "NEXUS_".

[MOD] Moved the initial values to WindowProgressBar.
[MOD] The WindowBase now takes x, y, width, and height to construct a
window.
[MOD] Removed the prefix of "NEXUS_".
[DEL] Removed useless statements in WindowBase.
Added WindowSilder.

[NEW] Added WindowSilder.
[NEW] Added window font setting to languages.
[MOD] Moved font initialization to WindowBase.
[MOD] Changed WindowMessage to new approach.
 Merge from master.
Merge remote-tracking branch 'origin/master' into window-silder

Conflicts:
	src/window/command.lua