[Build] Keep composer.lock and keep a .gitignore.dist

As we now ship with a working compsoer setup it makes sense to
also ship with the resulting composer.lock file. While at it also
provide a copy of our .gitignore file for optional use.
[Composer] Skip 2.3.14-15 becasue of #symfony/symfony/issues/10986
Merge pull request #158 from ezsystems/lock_n_ignore

[Build] Keep composer.lock and keep a .gitignore.dist