Minor changes to MainInstaller.sh

Added QL Plugins via the cask manager. These are based on my use of QL so you might not want to include them, but can very useful. 

When a new SSH key is generated it is also added to the system agent. Can make SSH with repos much much easier. Loaded on Terminal startup. 

Call `gcc` in the script, which allows a user to install command line developer tools with the need for Xcode so can cut down the bloat if Xcode is not desired. 

Added Android via brew is just easier and less effort to maintain. 

All tested and appear to be working on my mac.