Added patch for gromacs 4.6.2
Hid NL_STRIDE option in SecondaryStructure
CS2Backbone improvements:

- solved a bug with averaging over parallelized replicas
- more documentation
Merge branch 'v2.0' of git.assembla.com:plumed2 into v2.0
CSBackbone - more documentation
CS2Backbone: a lot of more documentation
cs2back gromacs example
cs2back gromacs example
cs2back gromacs example
cs2back example
Fixed neighborlist

Now getReducedList can be called more than once returning the same list
I also updated a regtest.
The previous test was only testing stride=2 (or, equivalently,
stride=20 into a trajectory with stride 10).
Merge branch 'fixing-nlist' into v2.0