User management search just searches users - adjust label of input field - fixes #10229
drop unneeded var_dump - fixes #9997
Merge pull request #12272 from owncloud/drop-var_dump

drop unneeded var_dump - fixes #9997
Merge pull request #12270 from owncloud/fix-search-label

User management search just searches users - adjust label of input field...
Cleanup config handling - deprecate old ways to interact with config

* deprecate old and static ways to interact with config
* introduce SystemConfig to avoid DI circle (used by database connection
  which is itself needed by AllConfig that itself contains the methods
  to access the config.php which then would need the database connection
  - did you get it? ;))
* use DI container and use that method in legacy code paths (for easier
  refactoring later)
* create and use getSystemConfig instead of query() in DI container