Improve description of Elytron mapped-regex-realm-mapper and simple-regex-realm-mapper

Description of Elytron mapped-regex-realm-mapper and simple-regex-realm-mapper for read-resource-description operation in JBoss CLI and in wildfly-elytron_1_0.xsd should be improved. Following information should be provided there for mapped-regex-realm-mapper:

• In case when username does not matches pattern and delegate-realm-mapper is used then result of delegate-realm-mapper is mapped through realm-map. Add this information to description of delegate-realm-mapper.
• In case when value for mapping is not in the map or in case when realm with name of value in to from realm-map does exist in given security domain then default realm is used.

Following information should be provided for both simple-regex-realm-mapper and mapped-regex-realm-mapper

• In case when more capture groups are obtained in pattern then first capture group is used. Add this information to description of pattern.