Added bc to the dependency list - not present on Ubuntu server 15.04
Added bc to the dependency list - not present on Ubuntu server 15.04

dicer/raspbian-ua-netinst,yodaaut/raspbian-ua-netinst,cybercircuits/raspbian-ua-netinst,beylsp/rpi-installer,daytonpid/FireHawk,kolargol/raspbian-ua-netinst,racing-tech/rrp-raspi-installer,beylsp/rpi-installer,malsony/raspbian-ua-netinst,matt2005/raspbian-ua-netinst,FooDeas/raspberrypi-ua-netinst,racing-tech/rrp-raspi-installer,firepick/FireHawk