Bug 1119802 - RFE: Support for resource type name change

Added displayName optional attribute to resource type. This does allow to
change resource type name (by specifying this attribute in plugin
descriptor) and at the same time does not require to drop & re-create whole
resource type on server when performing plugin upgrade. I've updated all
coregui code, to show displayName instead of just name, legacy gui was not
updated as it is no long used.
Merge pull request #98 from lzoubek/bugs/1119802

Bug 1119802 - RFE: Support for resource type name change