Map on 'presave' - not 'prepare'

FeedAPI calls node_object_prepare() on feed nodes before saving. It does this to give other modules a chance to add default values to the node object before saving. Feed Element Mapper bastardizes this behavior and does the mapping at this stage - which is a bad idea.

The proper stage would be 'presave' - AFTER a node has validated and BEFORE a node gets inserted or updated.

However, there may be problems with 'presave' as mappers may assume that mapping happens before 'validate'. A solution would be to add a direct call to _feedapi_mapper_map() to the node saving procedure in feedapi_node module.