Revert "Added new amber99sb-ildn-bsc0 force field."

This reverts commit 3f7bdff15b41f7e0ffbfd0bf86b9c677ae51db77.

This is a temporary measure, pending testing of this variant
that is comparable with that for other AMBER forcefields, and/or
resolution of questions raised on gmx-developers.

Also removed line from the manual that was generated when this force
field was in the repo.

Change-Id: I1c2269d2ed554b827fb183d54f1db789a5762a8f