faster implementation, calls scripts once

Slow implementation, calls scripts everytime

(cherry picked from commit ae6c8ee4)

Fixed regtest

See https://travis-ci.org/plumed/plumed2/jobs/354357664
cc @carlocamilloni

eds module - update one of the regtests to use lower precision restart output to make regtest more portable

Coverage scan is now stored in a separate repository. This allows
generating the manual and the coverage scan in two different travis jobs.

Since this introduces a new travis job (for coverage scan), I removed another
job that was redundant (build with mpi and -O3; notice that we always use -O3
since v2.4). System lapack are now tested on the first job.

Fixes #348

This will decrease the number of pull requests from PlumedBot.

Currently, everytime a file is updated and someone forgets to run
headers.sh, the headers are outdated. With this change, this will happen
once per year. PlumedBot will thus mostly fix erroneous copyrights
(rarely happening).