graphics/fly, net/concourse-fly: Mark both ports as conflicting

They both install bin/fly.

While here, fix errors reported by portlint(1) in net/concourse-fly:

• Quote install to hint that the port is not using install(1)
• Replace rm by ${RM}
• Move bsd.port.mk include to the last line

Reported by: rodrigo@ (ports conflicting)