WFLY-2468 WFLY-1469 WFLY-160 add support for runtime reloadable mail operations

mail subsystem changes:
- new model version 2.0
- new parser version 2.0 & xsd
- better runtime operation tests
- all operations are runtime executable now
- update XSD & default confguration

WFLY-2468 MappingModuleDefinition is incorrectly constructing the write-attribute handler