MDL-12698, MDL-12569 - componentlib & langimport improvements and fixes; merged from MOODLE_19_STABLE

Reports now don't need mod.php but they should include the admin headers/footers.

There are undoubtedly bugs in this but this framework should be more sane

deglobalization of $ADMIN; merged admin/adminlib.php into lib/adminlib.php; fixed includes and some other minor fixes

cleanup in admin/index.php; preparation for health center, loginas gui, password salts; merged from MOODLE_16_STABLE

download.moodle.org using the component_installer class.

Seems to work at the fist try, so something is wrong, sure! :-P

moodle versions... PostgreSQL people, check it against your
servers, please.
In 1-2 days I'll merge this changes to 15_STABLE, to allow
moodlers to pre-check their environments...

to its minimum for now.

It's the only one to be used from the rest of code.
Changed recommended to optional.

can be checked, so I commit this.
Just starting to build the presentation layer of the stuff.