Do not create markers at internal attribute validation by XModel

This framework needs improvement/refactoring. It was created before WTP validation framework and is not integrated into it. In many cases problem markers created by our validation duplicate markers created by WTP validation.
It is ok to have some internal validation for model consistency, but it should not interfere with the standard framework. Markers should be created by delegates of the validation job.
Now, trees and forms of JBoss Tools editors recognize markers created by XModel and display them. We may try to replace this by
1) either to be able to bind any markers with model objects
Profit: that would immensely improve displaying problems in tree/form in JBoss Tools editors
Possible Minus: It may be very resource consuming;
2) or to store the found problems as internal objects, not as markers, and refactor editors/views to displaying them
Profit: Preserve feature at the current level
Minus: Developing internal framework that cannot be reused;
3) or just drop it
Profit: No need for development, just do not create markers.
Minus: Problems in tree/form in JBoss Tools editors will not be displayed. Also, other possible unexpected aftermath should be addressed to.