Expand battery 3

Stage 3 of expanding the test battery:

 * fix `get-global-config` bug for retrieving [something]here failing to print (isn't a dict so needs a print statement)
 * add testing for `get-global-config`
 * add section to site config for specifying hosts for testing directives on (see below)
 * add testing for loadleveler tasks
 * add skip test functionality to `test_header`

To run the loadleveler test (I think you have this?) you need to add the following to your `site.rc`:

```
[directive tests]
loadleveler-host = <LOADLEVELERMACHINE>
```

If you don't have that then the test is skipped (will return ok and not attempt to run that suite).

I would envisage that developers of the SLURM, PBS etc. routines would add tests for those submission methods, directives and kill commands, as appropriate, along the same lines to the loadleveler test using a similar suite and adding e.g. `01-slurm.t`. The code here lays the framework for them to create that in.