New ldapadmin module

Successfully tested on http://sdi.georchestra.org.

Some issues remain: #270, #268, #244, #242, #241, #240, #239, #238, #237, #236, #235, #234, #233,#216, #215, #214.

See related PR: https://github.com/georchestra/template/pull/5

Maybe we should add a new UPGRADE.md file at georchestra root. In the case of ldapadmin, various new install steps are necessary.

Thanks to @pgiraud, @mpazos