rose suite-run: ROSE_VERSION and CYLC_VERSION

Resolve #710.

This change allows ROSE_VERSION and CYLC_VERSION to be specified in `rose-suite.conf` like so:

```cfg
[env]
ROSE_VERSION=2013-06
CYLC_VERSION=5.3.0
```

On `rose suite-run`:
* If `CYLC_VERSION` is specified, it will export the specified `CYLC_VERSION` before calling any `cylc` commands.
* If `ROSE_VERSION` is specified and does not match the version being used, the command will fail. (The version must be the actual version string, i.e. `next` is not supported at the moment.)

N.B. `rose suite-stop` and `rose suite-gcontrol` would already export `CYLC_VERSION` to the correct value. `ROSE_VERSION` for those 2 commands are unimportant.