Moved backup/restore doc to own file, since it's quite extensive.
Added note about out of date documentation.
Moved development setup to own file.
Added some doco relating to high level domain concepts, mainly for the benefit of other developers who want to work on AATAMS, but @kereid might also find it useful.
Some comments on grouping of receivers and tags.
Merge pull request #79 from aodn/high_level_doc

High level doc