Add cell array of strings utilities.

Two new utilities are provided:

`cellStrCat` - Creates a new cell array of strings from a list of cell arrays
of strings by concatenating each cell of input i+1 with each cell of input i.

```
>> cellStrCat({'a','b'},{'1','2'},'_',{'x','y'})

ans =

    'a1_x'   'a1_y'   'a2_x'   'a2_y'   'b1_x'   'b1_y'   'b2_x'   'b2_y'
```

`num2cellStr` - Converts a numerical array (of any dimensions) into a cell
array of strings of the same dimension.

```
>> num2cellStr(1:4)

ans =

    '1'    '2'    '3'    '4'
```
Add help for `cellStrCat` and `num2cellStr`
Fix inconsistent 'grow cell array in loop' style
Make contact sensor state/output names different
adding euler angles to forwardJacDot (matlab only for now)
implemented Jdot for euler angles (mex and matlab)
adding simple test to test consistency between Jdot w/rotations in matlab/mex
fixed call to forwardJacDot. I think this is the only example that was using the robotnum argument
working changes, added LU decomp and some timing printouts
removed timing code
implemented recursive algorithm from Orin, Goswami, Lee (2013) in matlab
mex'd recursive CMM algorithm
display optional in momentumTest script
removing backup file
Changed contactConstraints so that phi = <relpos,normal>, instead of phi = sgn(<relpos,normal>) * ||relpos||
updates to RB and RBM to support assymmetric effort limits
removing redundant check
Qy in zmp tracker now gets passed to tilqr
silenced printout in trajectory class
Merge pull request #68 from kuindersma/asymmetric-effort-lims

Added support for assymmetric effort limits