Allow deprecated header in Plumed.h (needed for next commit)

Compute extra CVs in MD code

opMap is now constructed in a single statement. This avoids
problems possibly arising with multiple threads accessing for the first time
to this method simultaneously.

opMap is then made const for clarity.

(cherry picked from commit 10cbe7e8)

Fixed the initialization of some static data by treating them as
static vectors and initializing them with a lambda function.

In principle, this rules out possible problems arising when multiple threads
call the decode function simultaneously for the the first time.

The vectors are then declared as const for clarity.

opMap is now constructed in a single statement. This avoids
problems possibly arising with multiple threads accessing for the first time
to this method simultaneously.

opMap is then made const for clarity.

It is not completely clear what would happen with multi threads.
Since the function is not used anywhere, I just remove it.

cc: @valsson

Fix for bug in TD_GRID

Fixed typo in grid spacing lookup

See merge request MPIP-Valsson-Group/plumed2-ves!4

* copying and adapting the FaMetaD code from the old version, still need to be tested

* forgot keywords

* fixed a few things in the FaMetaD

* improved parsing, error msg, and log printing

* moved updating of pace to update()

* astyle fix

* made FaMetaD work with current acc cacluations

* regtest for FaMetaD

* added printout of reading in of acc value

* fixed a newline error in acc printout

* added manual info for FaMetaD

* astyle fix

* removed not needed values from colvar file in rt

* fixed a problem with restarting of FaMetaD

* added rt for restarting of FaMetaD

* add notes to the manual on restarting and acc factor

* fix for restart regtest for fametad

* added warning if restarting and not reading in acc from file

* astyle fixes

* Added a check to make sure that combing FaMetaD and MPI mwalkers is not allowed

* changed error call to be consistent

The list is now shorter, only include very common compilers, and is consistent
in C and C++. In particular, on OSX it chooses both clang++ and clang as default.

Fixes #375

Allows embedding a separate PLUMED instance.