Navigation has now been re-ordered in accordance with http://docs.moodle.org/en/Development:Navigation_2.0_structure.
This has led to several changes in the way in which navigation is generated included API changes, most notably using the
navigation_nodes add method now returns the newly added node rather than the key.
At the same time the global_navigation_tree block has been renamed to navigation and settings_navigation_tree to settings.

This is highly useful when developing or debugging any emailing feature.
I am going to backport this after the end of the current Ice Age.

MDL-16658 restore - new restore:createuser cap + pre-check users before restoring; merged from 19_STABLE

backup/nopasswords MDL-20383 Backups are now never saved with user passwords unless the admin has defined $CFG->includeuserbackupsinpasswords in config.php  (Merged from 1.9)   Credits to Eloy

MDL-20700 coding style cleanup - cvs keywords removed, closign php tag removed, trailing whitespace cleanup

MDL-19039 improved default frontpage role capability evealuation, needs to be manually enabled in config.php

This is part of http://docs.moodle.org/en/Development:Theme_engines_for_Moodle%3F

$THEME is now initialised at the same time as $OUTPUT. Old functions like
theme_setup are deprecated in favour of methods on $PAGE. There is a new
theme_config class in outputlib.php that deals with loading the theme config.php file.

CSS used to be served by themes styles.php files calling a function in weblib.php.
Now it works by each theme's styles.php file doing
$themename = basename(dirname(__FILE__));
require_once(dirname(__FILE__) . '/../../theme/styles.php');
which is less code to be copied into each theme. (Old-style styles.php files still
work thanks to some code in deprecatedlib.php.)

Admin UI for choosing a theme cleaned up.

A couple of theme-specific hard-coded hacks like $THEME->cssconstants and
$THEME->CSSEdit have been replaced by a more generic $THEME->customcssoutputfunction
hook. See examples at the end of outputlib.php

Also:
* Fix setting the theme in the URL, which seems to have been broken since 1.9.
* Fix up errors on a few pages caused by the new initialisation order.
* MDL-19097 moodle_page::set_course should not set $COURSE unless it is $PAGE.
* httpsrequired() from moodlelib.php moved to $PAGE->https_required().
* Move has_started() method to the renderer base class.
* Further fixes to display of early errors.
* Remove print_header/footer_old from weblib. I did not mean to commit them before.

MDL-17849 sql queries not printed by default during upgrade anymore, there is a new config.php only setting $CFG->upgradeshowsql instead

MDL-16483 $CFG->unittestprefix not required anymore to run unit tests that do not need fake db; it should be saer to let admins modify the prefix in config.php instead of modifying it from php

MDL-17754, MDL-11061, MDL-9276, MDL-17777, MDL-17787 - various url handling improvemetns; rewritten $FULLME and added $ME, $SCRIPT and $FULLSCRIPT; improved slashargument handling especially for IIS; removed legacy slasharguments functions obsoleted since 1.6; some other refactoring; reverse procy support, ssl appliance support

MDL-14589 initial file storage implementation, temporary file manager, migration of course files; blog conversion MDL-15905; assignment conversion MDL-15904; fromslib  related file improvements MDL-15906

Can now override the public key lifetime by specificying value
for $CFG->mnetkeylifetime in config.php

Merged from STABLE_19

out from the XMLDBEditor, ignoring the prev/next stuff, that will be
automatically regenerated by the Editor by simply loading and saving
the edited file. Credit goes to skodak!

xmldb: added $CFG options for disabling next / previous value checkings & enforced comment checking. merged from mahara :)

we are going 100% unicode now - removed use of $CFG->unicodedb and current_charset(); MDL-7439 - part 2, only hotpot and wiki left