Move the e2e tests out of make check

Force LANG to en_US when generating biboumi.spec (fixes the date format)

Fetch Catch from our own clone, instead of the github one.

Avoids:

- Relying on github’s services
- Fetching a new (malicious) version, automatically, without any “check”

Add a basic integration test in python

Add a “rpm” target in the makefile, building a RPM

Spec file becomes a template, auto filled with the date and version

Fix a build when litesql is found but not botan

fix #3157

Only activate systemd’s watchdog if we are compiling with systemd

ref #3152

Display an info message on make dist

Install the unit file in lib/, not etc/

Include catch.hpp in the dist tarball

If catch.hpp is found in tests/, use it without cloning the git repo

Remove the second '-' from the package when ~dev is there

Build the doc with the default make target

Generate systemd file from template and make installs it and the conf

The unit file Type=, as well as the executable path should now be correct
with a simple “make install”, whatever the install prefix and the DESTDIR
values are.

ref #3152

Only include the coverage flags when compiling with gcc

Only download Catch when the test_suite target is built

Make lcov gcov etc optional

make coverage will display an error instead

make coverage is only available with a debug build

Add code coverage support

make coverage runs the test_suite and generates a report