Changes to um-setup to allow GCOM to install with Cylc 8

[theabro]

Following from GCOM:#242, GCOM will only be able to be installed with Cylc 8. As the um-setup script installs from the head of the GCOM trunk by default, this will cause problems when running this script after GCOM:#242 is commited unless Cylc 8 can be used.

The changes in um-setup have been made to:

1. Maintain the directory structure of the GCOM install as done under Cylc 7, to minimise changes needed elsewhere in the script.
2. Keep Cylc 7 as an option when needing to install older versions of GCOM (the -c 7 option)
3. Provide Cylc 8 as the default behaviour (although running with -c 8 will also make use of Cylc 8)

After Cylc 8 is used to install GCOM, the Cylc version is set back to 7 for use with ShumLib.

It may be best to not commit this pull request until GCOM:#242 has been commited, but to do so as soon as possible thereafter.

UM ticket um:#7839 will update UMDP X10 documentation on how to install and run the UM on the VM.

When Cylc 8 is used, additional information is given when the um-setup script is run:

INSTALLED gcom_install from /tmp/tmp.nxxEAXDBBI/wc/rose-stem
INFO - Workflow: gcom_install
INFO - Scheduler: url=tcp://vagrant:43001 pid=169780
INFO - Workflow publisher: url=tcp://vagrant:43092
INFO - Run: (re)start number=1, log rollover=1
INFO - Cylc version: 8.3.6
INFO - Run mode: live
INFO - Initial point: 1
INFO - Final point: 1
INFO - Workflow shutting down - AUTOMATIC

This has been tested with Andy Malcolm's vn8.3_cylc8 branch with UM13.7. This has been tested with rose-stem and all jobs completed successfully.

The command

um-setup -s fcm:[email protected] -g fcm:gcom.x_br/dev/andymalcolm/vn8.3_cylc8

was used to install GCOM. To install the current GCOM head of trunk, the following command was tested, and GCOM installed successfully

um-setup -s fcm:[email protected] -c 7