Update / README and template changes

[ImreSamu]

Changes/Proposals:

• improve README ( with security, troubleshooting, .. )
• improve LABEL
• Alpine: add BASE_IMAGE ( using with other base images )
• Alpine: extend testing ( now it is similar than the -master )
• make update ( regenerate docker files from templates )

EDIT:

• adding cunit-dev;git to the alpine build

removing this warnings:

checking for CUNIT... no
configure: WARNING: could not locate CUnit required for unit tests
...
/usr/bin/perl ./utils/repo_revision.pl
Can't determine revision: no git executable found

EDIT2:

• in *-master template : fix lto and add cunit

[ImreSamu]

Ready for review.

[ImreSamu]

Thanks for reviewing! Yes, it's ready to merge.