This enforces proper types on POST and GET arguments where I considered it sensible. I didn't update some as I don't know what kind of values they would support 🙈
Fixes https://github.com/owncloud/core/issues/14196 for core
remove unused methods
split mapping methods off from Access class
fix DB query handling
move 'clear mapping' methods from static helper to new mapping class
add tests
test directly with DB
finishing tests and fix return value from setDNbyUUID
add corresponding class for groups and make abstract test class neutral. helper tests is now obsolete as the tested functions were moved to the new mapper class.
add missing info to PHPDoc
add unmap method
fix namespaces
fix test inheritance
PHPDoc and a small code restructure for scrutinizer, no effective changes
PostgreSQL does not accept LIMIT in DELETE queries
phpdoc fixes, no code changes
