Changed loadModels() once again. Removed loading of models based solely on model filename. Added support for different models with the same file names. All models files are required, in order to determine class names. The changes result in an overall increase in flexibility with respect to model file names.

Doctrine_Query_Tokenizer::bracketExplode() were case sensitive, and 
changed tokenizer to make them case insensitive.

Introduced a new attribute ATTR_AUTOLOAD_TABLE_CLASSES that can be used to control whether Doctrine should try to autoload custom table class files when looking for them.

Ticket: 650

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- Fixed problem with Nested Set table definition not happening in time for exporting when NestedSet behavior is added through Doctrine_Template_NestedSet.

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The default is set to false because fetching the relations deletes
previously fetched relations =P. This is, if you fetched an aggregated
value (SUM, COUNT), it wont be refreshed, it will be overwritten by the
actual related values.