Issue #365: use global composer command if composer already installed globally
Generate supported locales files and Gaia versions from external JSON source

* PHP script to extract supported repos and locales
* Remove old sources (*.txt) and move l20n_text.txt in config/sources
* Update scripts, rename iniparser.sh to bash_variables.sh, move config.ini conversion to bash to scripts
Merge pull request #363 from flodolo/externalize_sources

Generate supported locales files and Gaia versions from external JSON source
Merge pull request #366 from pascalchevrel/issue365-fix_call_composer_global

Issue #365: use global composer command if composer already installed gl...