Add updated regional missense constraint estimates for v4 to browser

[gtiao]

[nawatts]

Is this different than #603?

[gtiao]

No -- I suppose I wanted to clarify that we want to do this on v4 specifically, since it will be a much larger dataset than the previous exome release and should give us increased power for refining regional missense constraint (i.e., increase the likelihood of finding meaningful differences in RMC values). I'm not sure yet if it makes sense to do this for v2.1 data, although that will be available sooner. It depends on whether there is bandwidth for tweaking and improving our approach to searching for sub-genic boundaries of constraint.

[nawatts]

Updated styles for the regional missense constraint track are in the regional-missense-constraint branch.