Make powered by false by default. Remove unused poweredby from side nav theme. Tweak spec for signin top logo to remove requirement for src.
Make powered by false by default. Remove unused poweredby from side nav theme.
Tweak spec for signin top logo to remove requirement for src.

learningequality/kolibri,learningequality/kolibri,learningequality/kolibri,learningequality/kolibri