This patch replaces all homegrown timezone
stuff with standard PHP date/time code.

The main change is the introduction of core_date
class that returns normalised user and server
timezones. From now on nobody should be using
$CFG->timezone or $user->timezone directly!

Other new features and fixes:
* admins are prompted for timezone during install
* editing of other users is finally fixed
* timezones are displayed in user profile
* new $this->setTimezone() in phpunit
* time locale is now automatically reset in phpunit
* timezone is now automatically reset in phpunit
* phpunit has Australia/Perth as default timezone

This reverses the references used for global $USER and $SESSION,
the reason is that PHP does not allow references to references.
$USER is a reference to $GLOBALS['USER'] which means we cannot
put any references to it. Solution is to store the current user and session
objects in $GLOBALS['USER'] and $GLOBALS['SESSIOn'] are reference
them in $_SESSION.

This patch makes the session code behave the same way in CLI,
phpunit and normal web requests - this allows use to finally
unit test most aspects of the session code in Moodle.

Includes:
* update checker refactored to \core\update\ namespace
* plugininfo classes refactored to \core\plugininfo\ namespace
* plugin_manager renamed to core_plugin_manager
* redirect back to original page after plugin uninstall
* fixed assign subplugin uninstall
* move assign subplugins under the assignment in admin tree
* fixed plugininfo for all question related plugin types
* auth uninstall support
* added missing block dependencies
* added theme uninstall
* subplugin types are following the plugin on plugin overview page
* several performance improvements in plugin manager
* new warnigns when plugininfo are outdated or missing
* multiple fixes and other improvements

Improvements include:
* Alternative location might be useful when server administrator wants to maintain
  a local copy of component cache instead of using shared $CFG->cachedir.
* Component caching is now enabled in behat tests which should improve performance.
* Standardised ignoring of component caching.
* Fixed debug mode in ABORT_AFTER_CONFIG scripts.
* General documentation improvements.

There were multiple problems discovered.

This reverts commit 5c92e7a7.

Conflicts:
	admin/cli/install.php

This should resolve all problem on developer machines when switching branches or when restoring previous Moodle databases. It also prevents any potential problems during upgrades such as concurrent DB modification and resolves chicken egg problems in future caching upgrades.

This fixes column width issues and compatibility with RTL languages.

PARAM_TYPE can not be used for full OS paths. Admins have to enter correct data there, if not they get directory creation error.

PARAM_TYPE can not be used for full OS paths. Admins have to enter correct data there, if not they get directory creation error.

Signed-off-by: Aleksey Avdeev <solo@altlinux.ru>

Instead of using the default dataroot location, the tempdir and cachedir
are now set under the real dataroot location specified via the argument
and/or the interactive session.

The patch also adds a PARAM_PATH check for the dataroot specified.

This fixes the patch f848c0f6 introduced
in MDL-29351.