Document how to use Amber

[MarionBWeinzierl]

Talk to James Gebbie about access to Amber and add the info to the docs

[ptheywood]

67 adds very basic amber docs, at software/applications/amber.rst.

Additional, more detailed docs can be added to this file once it has been approved and merged on actual amber use (ideally by someone who has used amber)

[ptheywood]

Now #67 is merged, the very basic Amber documentation can be exapended by editing software/applications/amber.rst

[ptheywood]

Closing this as the docs taskforce is being closed, and minimal amber docs are present. The docs page can still be expanded if required with bede-speicifc additions if required.