Added SLURM and Conda support

[xchoo]

Added SLURM, and alias support for CI scripts.

• Modified exe function in base_script.sh.template to support aliases
• Modified remote-script.sh.template to perform docs tasks for any script ending in "docs"
• Added SLURM support with slurm-script.sh.template
• SLURM support wraps given commands with SLURM commands using bash aliases
• Note: slurm-script supports aliasing of generic commands, while changes to exe function support aliasing of commands called with exe
• Added usage instructions for slurm-script.sh.template and remote.sh.template
• Updated secret.tar.enc to use abrghost instead of abrgl
• Added remote slurm test script as an example

How has this been tested?
Tested by running test suite. Also checked that slurm runs are being executed properly.

How long should this take to review?

• Quick (less than 40 lines changed or changes are straightforward)

Where should a reviewer start?
Start with slurm-script.sh.template

Types of changes:

• New feature (non-breaking change which adds functionality)

Checklist:

• I have read the CONTRIBUTING.rst document.
• I have updated the documentation accordingly.
• I have included a changelog entry.
• I have added tests to cover my changes.
• I have run the test suite locally and all tests passed.

Still to do:

[xchoo]

Okay. I think this is pretty much stable now. I left the slurm-script the way it is since it seemed to be the only way generic commands (in the wrapped script) worked with the aliases. The changes to exe does give it support for SLURM, so if we can guarantee that every command in the wrapped script is run with exe, we can remove slurm-script.