initial commit of instructions for building from source, addresses #22

This page needs additional material detailing options available
slightly tweaked instructions in response to Zultron
fixed file name, changed next_section pointer, edited _data/doc.yml

These changes place "Building from Source" in "Development" submenu
take advantage of the command option 'su -c'
Merge pull request #26 from RunningLight/BuildInstructions

initial commit of instructions for building from source, addresses #22