Fix misplaced `isempty(t)` in `inverseKinBackend`
Add hands to `atlas_chull.urdf`
Add MinDistanceConstraint.

Adds MATLAB and mex versions and adds it to `testKinCnst`
Get testKinCnst to pass for MinDistanceConstraint

Had to set `num_constraint` in the MinDistanceConstraint constructor and pass
`true` for `always_use_mex_dynamics` in the `MinDistanceConstraint` section of
`testKinCnst`.
Remove conflict markers from RigidBodyConstraint.h
Switch to smooth hinge loss in MinDistance

The new penalty function for dist < 0 is

penalty = -x*exp(1/x)

This looks like a linear function (slope -1) as dist goes to negative infinity
and has all derivatives going to zero as dist goes to zero. Thus the piecewise
function formed by setting penalty = 0 for all dist >= 0, is infinitely
differentiable.
Remove commented code from MinDistanceConstraint
Convenience fxns from RussTedrake/floatingBase
Add getCMMdA

This is a `geval`-compatible version of `getCMM`. I think it should end up
being called `getCMM`, but I don't want to go through and change all the
current uses of `getCMM` to `getCMMAdot` in the DRC codebase right now.
Add toLCMGL method to `RigidBodyBox`
Remove `l_hand` from `l_arm` group
Add getCMMdA method for RBM.

Also adds `testGetCMMdA`.
Add WholeBodyPlanner and test.
Add WeightedSquaredError and test
Add WeightedSquaredFirstDiffError and test
WholeBodyPlanner uses weighted sq. error clases.
Remove printouts from MATLAB MinDistanceConstraint
Add v as decision variable in WholeBodyPlanner
Add sole frames to atlas_chull.urdf
Special case TSRBM in kinematicPathJoints  ...

in WorldEulerConstraint and WorldPositionConstraint.