Install scripts via python

Background:
* Our current install scripts duplicate a lot of logic with platform-specific commands.  
* In addition, our scripts ask for input towards the end of the scripts, rather front-loaded at the beginning so that a user could walk away and have the script complete
* Existing scripts do not allow users the option to install clean over an existing install
* Existing scripts do not have a non-verbose / noinput option.

Design:
* Create an "install" Django command that can be run anytime to (re-)install KA Lite.
* Call the command from the OS-specific scripts, once Python has been detected
* Tried to extract out platform-specific operations into a single file (which are added to in other branches)

Testing:
* Done only on MacOS
* Tested using `install.sh` and `python manage.py install`

Notes:
* Moved some apache-specific permissions changing into the apache config script 
* This addresses issue #97 (partially) and #260, and enables us to address #261