copied Entity_Collection from wsCore.
modified for new EntityInterface.
made EntityAbstract an abstract; set model as static
and added a method to retrieve the static method name.
some initial implementation of EneityManager.
trying to find an easy way to get modelName from static class.
made EntityAbstract abstract.
added setSystemId to set id from database (after insert).
added save entities.
small fixes; register entiteis after new/fetch.