[BZ 1076126]  Move out from yaml to xml

Moved from yaml to XML representation of plugin-provided expressions. Now we
have XSD to generate JAXB classes and also to validate when parsing. For
expressions with 'createByDefault=true': dynagroups being created are
attached to plugin (having non-null cannedExpression). Whenever this
dynagroup is changed (via API or UI) it get's detached from plugin (setting
cannedExpression to null). Also on plugin upgrade or first install, if we
find a detached dynagroup having same name as we are about to create, we
just log INFO message - this happens when DG got previously detached.
[BZ 1076126] Update Group Definitions UI to show DGs from plugins

When listing dynaGroups we now show additional first column having an icon
of user - in case of regular dyna group or plugin - in case definition comes
from plugin. When user edits plugin-based definition we also warn him once
he attemts to save such expression. Within this commit i18n messages for old
template names has been removed.