Update BUILD.md
Update BUILD.md

Overall clean up and correcting typos
kolargol/raspbian-ua-netinst,dicer/raspbian-ua-netinst,yodaaut/raspbian-ua-netinst,beylsp/rpi-installer,racing-tech/rrp-raspi-installer,firepick/FireHawk,Zeerix/raspbian-ua-netinst,cybercircuits/raspbian-ua-netinst,FooDeas/raspberrypi-ua-netinst,matt2005/raspbian-ua-netinst,daytonpid/FireHawk,racing-tech/rrp-raspi-installer,jturner314/raspbian-ua-netinst,malsony/raspbian-ua-netinst,beylsp/rpi-installer