run optimize during install, autodetect RPi hardware, tidy optimizerpi script
create simple 502 page for nginx, pull nginx's port config from settings
fix installer logic, tidy up some installer word-wrapping
improve optimizerpi validation.  Fix RPi discovery in settings
do not write wget response to disk
Merge remote-tracking branch 'leq/release-0.11' into autodetect_rpi

Conflicts:
	kalite/management/commands/install.py
Merge pull request #916 from gimick/autodetect_rpi

Autodetect rpi, improve nginx config