Prefix 'dendrite-' onto dendrite binaries (#47)

This distinguishes them from tools like 'kafka-producer'
which are not required to run a dendrite server.

The prefix also groups together the dendrite binaries nicely
on `ls` as well as making it nicer to tab-complete.

src/github.com/matrix-org/dendrite/cmd/roomserver-integration-tests/main.go

@@ -203,7 +203,7 @@ func testRoomserver(input []string, wantOutput []string, checkQueries func(api.R
 		panic(err)
 	}
 
-	cmd := exec.Command(filepath.Join(filepath.Dir(os.Args[0]), "roomserver"))
+	cmd := exec.Command(filepath.Join(filepath.Dir(os.Args[0]), "dendrite-roomserver"))
 
 	// Append the roomserver config to the existing environment.
 	// We append to the environment rather than replacing so that any additional

travis-test.sh

@@ -3,7 +3,7 @@
 set -eu
 
 # Check that the servers build
-gb build github.com/matrix-org/dendrite/cmd/roomserver
+gb build github.com/matrix-org/dendrite/cmd/dendrite-roomserver
 gb build github.com/matrix-org/dendrite/cmd/roomserver-integration-tests
 
 # Run the pre commit hooks