Merge pull request #71 from jklimke/fix_null_value_assignment_for_NSDate_columns

checked whether the value to set is nil and return @"null" as sql repres...
 * enabled usage of database views as base for an active record object
Merge pull request #72 from jklimke/enable_using_database_views_as_tables

 * enabled usage of database views as base for an active record object
Merge branch 'master' of https://github.com/AlexDenisov/iActiveRecord into definable_foreign_key_names