Warning on GHOST

Addresses #74 (warning only)
typo in manual
Couple of fixes to 'plumed mklib'

(cherry picked from commit 2ccba594d5839167ec4e3f570b8c63f5a61b8d3c)

    Backported changes from master to fix "plumed mklib"

    There was a problem with Makefile.conf as produced with ./configure
    if used in v2.0. This fix allows to use new Makefile.conf with old
    (2.0) plumed.

    This should fix the problem with rt15 mentioned by Gareth in
    the discussion of #76

Conflicts:
	src/config/Makefile
Fixed #73 (problems with --version)

The only way to have something working has been to include a "VERSION"
file in the root dir which should be updated by hand when releasing.
Additionally, plumed --git-version can be used
Changelog
Fix #79

I changed the behavior of METAD INTERVAL in such a way that the bias
is correctly set to the value at the boundary when the CV is outside
of the interval. This changes the behavior of plumed when using
METAD INTERVAL and any sort of replica exchange (e.g. bias exchange).

Before the fix the bias was incorrectly set to zero outside the
interval.

* NOTICE THAT THIS BEHAVIOR IS DIFFERENT FROM THAT IMPLEMENTED
  IN PLUMED 1*
Regtest
Added component registering

All components now have to be registered in registerKeywords so that
documentation on what componets are available in a given action are
available in the manual.  Currently the code gives a warning if a user
tries to use a component that is not properly described in the manual.
In the future (v2.2) this warning will be replaced by an error.  That
is to say you wont be allowed to use unregistered components.  This is
all described more in #76
Added documentation on component registration.

Also took the opportunity to fix a couple of errors in other parts of the
developer documentation
ABMD: documentation updated for the components.
Typos
Better fixes #79

I improved the fix to correctly updated the grids far from Gaussian centers.
Fixed regtest

I also changed it to test potential far away from the border
Merge remote-tracking branch 'fix-79' into v2.0
Version number set to 2.0.2
Fixed changelog
Fixed script that prepares the release tar.gz
Merge branch 'v2.0' into v2.0-hrex