easyLDAP_TLSReqCert re-writing: Also tolerate boolean and strings for specifying the LDAP TLS ReqCert level.

easyLDAP/easyLDAP_defaults.py: Assure that EASY_LDAP config dict can be used for configuring TLS, as well.

easyLDAP_object: Provide refresh_cache() method option that prevents from auto-creating accounts for DNs that don't exist on the LDAP server.

easyLDAP/easyLDAP_class_cache.py: Fix for case where use_cache_history is False on contruction of easyLDAP_cachetree.

easyLDAP_cache/easyLDAP_object: Assure that cache history updates only occur if something got really changed. Also assure that only one cache history items gets added per atomic call to the easyLDAP_object instance's methods.

easyLDAP/easyLDAP_class_{object_base,cache}.py: Support injecting a cache_history stored elsewhere on instantiation of an easyLDAP_object.

easyLDAP_utils: Add make_pyldapobject() function (adapting LDAP dn-data 2-list elements to 2-tuple).

easyLDAP/easyLDAP_class_cache.py: Initialize use_cache_history and history size via easyLDAP_cache_history constructor.

easyLDAP/easyLDAP_class_cache.py: Fix for case where use_cache_history is False on contruction of easyLDAP_cacheobject.

easyLDAP/easyLDAP_class_cache.py: Always initialize easyLDAP_cache_history. This was the case already, but obfuscated by an if-clause that always evaluated as True.

easyLDAP/easyLDAP_class_tree.py: Assure that LDAP tree objects / attributes also contain values of type str.

 Completes bytes to str switch in 1133f6f9.

easyLDAP/easyLDAP_class_object_base.py: Catch variable usage before assignment in _modify_attrdesc().