Ground work for QML Widget themes

QML widgets are now easy to theme.  First, set the QPalette and then
call refreshPalette() to apply the theme.
Slightly changed the LedIndicator's colors because they are now taken
from the qApp()->palette() instead of being set separately. Also, I
slightly changed the contrast between the title and the background.  If
you want, we can talk about the contrast between them.

Related to Issue #43 (DOES NOT CLOSE ISSUE).