Added support for 'revision' parameter inside languages tags. Update cache only when needed. Re-enabled main() function. Added support for  <lang:link /> tags. Code cleaning.
Added support for 'revision' parameter inside languages tags.
Update cache only when needed.
Re-enabled main() function.
Added support for  <lang:link /> tags.
Code cleaning.

tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio