Improving validation support for studies reusing older studies/have multiple PRJ codes

[jfy133]

I've noticed more studies cropping up which the AMDirT validation checking isn't picking up or can't deal with.

Aida developed some pre-release checks that I recently extended (typically involving binding the libraries/samples tables together) which has picked up lots of things we have to list as 'exceptions'.

These are things such as re-use of data from previous studies, further sequencing etc. that have different PRJ codes than the 'primary' ones originally published; or re-analysis of studies not in the Dir (e.g. pop-gen)

These are currently implemented as (extremely rough!) Rscripts, and are listed here

https://github.com/SPAAM-community/AncientMetagenomeDir/wiki/Release-Procedure

We should

1. add these cross-tables checks to AMDirT
2. change schema/validation checks to adapt to existing 'exceptions'