Added tip5p to the list of watermodels in some FF.

Added support for flexible tip5p to OPLSAA and parameters
were taken from the Amber/Charmm tip5p.itp files.

There are, however, various problems with that water model.
This commit doesn't resolve them so the bug report below
will need to be followed up at later stage.

watermodels.dat now includes a note about these issues
and refers users to the redmine report.

Refs #1348.

Change-Id: I3adaae21f35efbb4240716e91f1bb5d256c8853e