Move MW install to composer.json

[simison]

composer.json should work as an entrypoint to MediaWiki + Extensions install, like this:

https://github.com/Hitchwiki/hitchwiki-docker/blob/master/composer-files/composer.json

Then extensions should follow this structure:

https://github.com/Hitchwiki/hitchwiki-docker/blob/master/composer-files/composer-wiki.local.json

Then: https://github.com/Hitchwiki/hitchwiki-docker/blob/master/scripts/docker-entrypoint.sh#L32-L49

...after this we can move some extensions out from bash file: https://github.com/Hitchwiki/hitchwiki/blob/master/scripts/bootstrap_vagrant.sh#L87-L94

[simison]

@Remigr:

...apparently SemanticForms is now called PageForms https://www.mediawiki.org/wiki/Extension:Page_Forms

[simison]

Done https://github.com/Hitchwiki/hitchwiki/commit/ab64348d83939de0b1a447d81747f6a0b1452745