Fix long delay with different window managers

Closes #6
https://github.com/mate-desktop/mate-netbook/issues/6
Remove trailing whitespace
Silence libtool warnings
Correct typo EXTRA_DIST for window picker applet
Fix EXTRADIST for maximus schemas
Add applet ui file to EXTRA_DIST
Applet, add gsettings_SCHEMAS_in_in var for EXTRA_DIST
Add CLEANFILES for distcheck