cmd/geth: changed version number to 1.2.0
cmd/geth: changed version number to 1.2.0

Changed the version number of geth to 1.2.0 so that dev builds are now properly build (instead of master). Note to self; increase version number to 1.2.1 for our next actual release.
maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum