Feature/subtrajectory

Implement getSubtrajectory for GlobalTrajectory and use it inside TimedElasticBand planning.

Also note #25 (closed) for the planToDest variable, as the free goal velocity when not planning to the end does not work yet.

Closes #13 (closed)

added hiwi local-planning labels

requested review from @fabian.reister

assigned to @groegerto

changed the description

approved this merge request

mentioned in commit 6069a50c

merged