doc: vale fixes, update TAL repeat object section. For repeat object/variable, added back first() and last() methods now that they are fixed. Moved start/end properties to separate property table along with index. Added details on how even works (e.g. even() is True when number() is 1 because the index is 0 which is even). Document returns from methods are mostly truthy and not true.

''' CGI interface modules '''
__docformat__ = 'restructuredtext'