Add extra properties to custom field theme functions

Problem/Motivation

There is currently no way to get raw values from custom fields in the preprocess functions for advanced theming.

Proposed resolution

For custom_field theme function:
Add the following:

#object (the entity object)
#entity_type
#bundle, 
#language
#raw_value (the raw field value)

For custom_field_item theme function:
Add: the following:

#entity_type
#bundle, 
#language
#raw_value (the raw subfield value including extra columns if applicable)

Note: The #raw_value for custom_field_item can be either a scalar or an array depending on whether the subfield type has extra columns.