#27 Subcorpus selection tags need to be specific to corpus in use

[S Luz]

Subcorpus selection tags should be specific to the corpus being used. A tag 'book' in GoK would be meaningless in OMC. This should be general across the tool, so all functions that refer to save subcorpora, including those in plugins such as comfree, should be corpus-specific. You could, for exmaple, prefix the tag with the copurs address (e.g. genealogies.mvm.ed.ac.uk:1241:books) and the dropdown menu under Sub-corpus->quick load should only display the subcorpora defined for the corpus currently in use.