Rename kite binary to kitectl and restructure the kite/cmd directory.

Lets be consistent against our -and with the rest of the world- tools and use `kitectl` instead of `kite`.

Kite package stays as is. Control applications name will be kitectl (like kloudctl and possible future fooctl's).
`github.com/koding/kite/cmd` package is also restructed for better readability. All subcommands resides in `kitectl/command` directory now.