Notification of string changes

Author: Jake Dallimore
MDL-79843 core: install/upgrade/admin supporting plugintype deprecation
This change:
- reports deprecated plugins during upgrade (informational only)
- reports deprecated plugins via site admin, permitting uninstall
- adds env check to block site install/upgrade when phase 2 deprecated
(deleted) plugins are detected. They must be uninstalled to continue.


http://git.moodle.org/gw?p=moodle.git;a=commit;h=2a0e5c9ec439faf3688fd3c7dc5a923134940f87
http://github.com/moodle/moodle/commit/2a0e5c9ec439faf3688fd3c7dc5a923134940f87

+ 5.0 en [deletedplugintypesdetected,core_admin]
+ 5.0 en [deprecated_type,core_plugin]