Rework internal of pkg_config, result bring better error messages,
Rework internal of pkg_config, result bring better error messages,

it also bring object resusable for plugins (WIP)

en90/pkg,junovitch/pkg,khorben/pkg,junovitch/pkg,en90/pkg,Open343/pkg,Open343/pkg,skoef/pkg,khorben/pkg,skoef/pkg,khorben/pkg