Merge branch 'feature/kostyantyn/e-acsl-gcc' into 'master'

New options and bugfixes in e-acsl-gcc.sh.

This merge request proposes the following changes in the `e-acsl-gcc.sh` script and related functionality.

- New `--rte` option allowing to annotate the source program prior to instrumentation.
- Fixed the issue that caused Frama-C/GCC paths be incorrectly computed is a path containing `~/` was used.
- Extra checks for required system utilities.
- Bugfix for issue #21. 
- Bugfix for issue #19. Note that there also exists one undocumented option (namely `--e-acsl-share` for specification of RTL sources), however the documentation for the option is omitted intentionally. This is an internal option that should be used by developers only (it is presently unused, so I am thinking of removing it).
- Basic bash completion file for the `e-acsl-gcc.sh` script.

See merge request !58