Refs #12636. Add doc. Add unit tests. Fix some bugs with 'single tick' replacement. New: double ticks in attributes are replaced by ''' - this guarantees that there are no more single ticks saved and the code is valid to be reused as variable inside QFQ Report.

Bug Fixes #11925. Form.parameter.downloadButton might contain now all parameter, incl. d, G, ... . KeyValueStringParser::explodeEscape() has been refactored. Function Link->paramPriority() has been renamed/rewritten to Link->paramPreparation(): double fire of explode() eliminated, code should be more efficient. Several new/enhanced unit tests.