MDL-29004 Wiki: display images in printer-friendly view
MDL-41291 cache: Use fread to avoid race conditions
MDL-36803 TinyMCE: Fix TinyMCE following touch events on iOS browsers
MDL-41380 backup: Fix incorrect function name from MDL-40618.
MDL-36126 backup: changed the message column in the table backup_logs to a text field to prevent DB errors
MDL-38505 Permit lesson to import images in question text
MDL-41245 fix multiple install, upgrade and uninstallation issues

Includes rework of cache parameter detection on admin/index.php.

Another problem is that uninstall does not leave system in consistent state,
we need to force users to go through upgrade after any type of uninstall.

This fixes also add-on installation redirect and other issues.
MDL-41022 cleanup core_ddl_testcase
MDL-41022 cleanup core_dml_testcase
MDL-41022 cleanup core_external_testcase
MDL-41022 cleanup core_files_file_storage_testcase
MDL-41022 cleanup core_files_zip_packer_testcase
MDL-41022 cleanup form tests
MDL-41022 cleanup core_phpunit_advanced_testcase
MDL-41022 cleanup core_phpunit_basic_testcase
MDL-41022 cleanup core_test_generator_testcase
MDL-41022 cleanup core_grade_category_testcase
MDL-41022 cleanup core_grade_grade_testcase
MDL-41022 cleanup core_grade_item_testcase
MDL-41022 cleanup core_grade_scale_testcase