Closes #354

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)

Fix for bug in TD_GRID

Fixed typo in grid spacing lookup

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

All atoms were erroneously requested also after the first step.

when using DEBUG, detailed timers were always shown by mistake.
Now they are only shown when using flag DETAILED_TIMERS

removed sentence about NOSPLINE

https://groups.google.com/d/msgid/plumed-users/4bdade66-5dde-4748-b3c2-3c6155906b69%40googlegroups.com?utm_medium=email&utm_source=footer

added syntax highlight in an example

Small fix: do not push manual when building from a pull request

(see 5c8e4631)

LDSHARED was erroneously reset in configure.