Adding secondary info for checking read and mapping quality

[bw2]

Looking at REViewer plots, I start wondering whether particular reads that contradict or support a give genotype are low quality. It might be useful if REViewer could (optionally?) draw extra info like:

• plotting some number for each read that describes mapping quality
• showing read pairs rather than reads
• whether a mate or a read pair was recovered from a distant locus
• read strand

[egor-dolzhenko]

Great suggestions! I will put together a proposal of the changes and, if you don't mind, run it by you.