Add dialog showing interpretability of target region

[marc-sturm]

Todo:

• add action to target region drop-down
• allow providing BED files of bad regions in GSvar.ini (low-coverage, low-mappability, ...)
• for each BED calculate overlap with target region - drop-down: exon+-20 or gene locus of relevant transcripts
• show interpretability of for each BED and overall value as table - one gene per row