This is a harmless mistake, I found it while implementing #653 so I backported the fix

cc: @valsson

This is an issue identified while implementing #653

It is not strictly necessary for PLUMED < 2.8, but I backported
it anyway for clarity and to avoid issue when people copy patches
from one version to another

See failures while testing #687

This reverts commit 3c316e1c.

See failures while testing #687

(cherry picked from commit 66363a3f)

(cherry picked from commit 34967ce1)

[doc] adding reference to modules configuration

Test numpy 1.19

See #656