[release_notes] add a row on 3D sound actuator
[release_notes] add terrain tools notes
[ci] travis: exit on error

use `bash -e` to exit the script on error
Add support for 'morse import <path>'

This allows to import pre-existing simulations in MORSE
for later run them with 'morse run' (or 'morse edit').

'path' must be a local path.

Partially fix #396
Added a 'quickstart' tutorial

It illustrates to use of 'morse create' and friends.

Partially fix #396
Implement a template for sensors

Used when calling 'morse add sensor ...'

Partially fix #396
[doc] Document in more places 'morse create|add'

Related to issue #396