New tests to determine and install previous version in upgrade stage

See merge request !37

Merge branch 'skip_upgrade_check_on_master' of gitlab.mythic-beasts.com:sympl/sympl into skip_upgrade_check_on_master

Skip upgrade check on master

See merge request !36

Improved backup scripts, added sympl-sqldump

Closes #217

See merge request !34

Resolves #232

See merge request !32

Changelog merge30

See merge request !31

Disable stats by default, improve security

Closes #220, #230, and #231

See merge request !30

Issue225 merge common to core

See merge request !29

Merge branch 'issue225_merge_common_to_core' of gitlab.mythic-beasts.com:sympl/sympl into issue225_merge_common_to_core