Add a user-friendly way to handle bidsmapping exceptions

[marcelzwiers]

Is your feature request related to a problem? Please describe. It is common for experimenters to have data acquisition exceptions. Currently there is no mechanism in BIDScoin to handle them

Describe the solution you'd like A way for users to compose a list of exceptions and define how they should be treated

Describe alternatives you've considered Write a postprocessing app but there is already fixmeta

[marcelzwiers]

Solved by adding a bidseditor context menu item that adds run-items with fully specified filepath and filename properties to make them selective for single (exceptional) data sources