Deleted hardcoded condition that brokes standart field validation process

Updated interface with nex dyncode

- webui now calls a hook to indicate a session end
- loader.py now set a lodel.dyncode module exposing dynmically generated code

- calling check_data_value on filters value to ensure value casting

	The UniqID datahandler has to call the datasource
	LeObject has to be able to determine wich parent class define its UID datahandler
	[NOT IMPLEMENTED] the datasource should be able to select with an abstract LeObject as target ( see #92 )

- datahandler base class was not supporting default values due to a bug
- implements the datetime datahandler construct_data method

Adding a field to all non abstract classes to store in DB the name of corresponding LeObject subclass

- Modified again the em_test to fit with testing purpose
- First test on multi datasource query written
- debugging of query.py

- adds tests on filter parse & check
 - standart filters parse & check
 - relational filters parse & check
- bugfixes related to tests in query.py
- update the example and the test EM
- bugfixes in admin script