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

Changes to e-acsl-gcc.sh (Issue #7 )

This merge request introduces the following updates:
   - Structural improvements to the `e-acsl-gcc.sh` wrapper script.
   - Options allowing to specify names of the Frama-C and GCC executables in `e-acsl-gcc.sh`.
   - Improvements of the documentation and the proper man page for `e-acsl-gcc.sh`. 
   - Convenience wrapper around `e-acsl-gcc.sh` to be used with testing (`scripts/testrun.sh`).

Julien, please have a look at the `scripts/testrun.sh`, it may implement some of the features that you may find useful need for testing. If you like the script I am happy to extend it with other features that may be lacking for the moment. 

See merge request !25