Fixed dependencies

Plumed.inc and Plumed.cmake are now regenerated each time.

(cherry picked from commit cff6770749e1bbe027460e1a1c9e3d98a45c4f69)
typo
Fixed header
Reference to published paper

Plumed paper has now a volume and page
Improved doc

I removed one page (WhatsNew) and merged it in the changelog page for
2.0
Improved doc for DISTANCE
Improved doc for ANGLE
Merge branch 'v2.0' into molfile_plugin
Changed a few ifdefs in molfile

This minimizes the difference between code with __HAS_MOLFILE
and code without it
Added proper check for molfile regtests

This allows them to be automatically skipped when molfile has
not been linked
Moved molfile regtest in a place where they are executed