Fix missing ti update in inverseKinBackend.m

`ti` was not being updated when parsing `PostureConstraints`
Add hands to `atlas_convex_hull.urdf`
Add MinDistanceConstraint.

Adds MATLAB and mex versions and adds it to `testKinCnst`
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.
Add setEvalHandle to FunctionHandleConstraint
Modify ABCDC and MDConstraint to respect kinsol

They now work with old-style mex IK and new-style IK, but not with old-style
MATLAB IK. They'll throw a sensible error in that case, saying that they need a
kinsol with mex enabled.
Add ABCDC and MDConstraint to testIK.
Fix for failing examples/Atlas/testIKGaze
Remove over-the-top path utils
Merge pull request #213 from avalenzu/MinDistanceConstraint

Min distance constraint