This reverts commit 0ed75e9d.

I changed the code in private convertTo* functions to the original
form (return bool). This is actually faster when exceptions are raised
frequently. In this manner, I solve the performance issue on Linux.

See #717

Error is this one:
../maketools/makelinks.sh: line 24: echo: write error: Broken pipe

It's triggered by the comparison with a <(echo) file, since the comparison
might fail before echo completes. If this works I will backport it

This reverts commit cc471663.

minor improvements to OPES_EXPANDED

minor improvements to OPES_METAD

In this manner later we could make the two modules independent

probably these writes should be formatted to avoid inconsistencies
btw compilers

Not used yet, but could be useful

See https://github.com/plumed/plumed2/pull/708#issuecomment-871624325

Otherwise, it is not possibly to copy correctly arrays of plumed objects

There are currently problems building with latest intel

Fix incorrect EXPANSION module in manual

trigger build

They are analogous to their C++ counterpart and should be used with care.

decref has also an optional argument (to) to decrease the number of
references to a given number. Can be used as a workaround for buggy
compilers such as gfortran