Merge branch 'kostyantyn/docs' into 'master'

Documentation for the E-ACSL wrapper script

Merge request addressing issue #6 

- Fixed a minor bug in the `e-acsl-gcc.sh` script.
- Added a section on the use of the E-ACSL wrapper script to the E-ACSL user manual. I placed the section at the very end of the manual, this is such that one first explores the available options and then learns how to make simplified runs. I think that the section on the wrapper script can also be placed at the very beginning (e.g., simple use with `e-acsl-gcc.sh` first and the advanced use via custom `frama-c`/`gcc` commands later). Please advise if the latter one is preferred. 
- Added an entry to the Changelog regarding the above change.
- Fixed test failures due to changes in the output of `frama-c`.

See merge request !26