Backwards-compatibility if someone used this anywhere
Fix some typos in tablebase
Properly initialize TableFiller.__possible_field_names__ only if needed
Allow TableFiller.__possible_field_names__ to be a dictionary with values
specific to each column.
Adds a new modifier for the fallback defaults to use when there is a
dictionary, but no value for the current column.
Includes test cases for all changes in fillerbase.
Rename FormBase.__dropdown_field_names__ to FormBase.__possible_field_names__

Includes deprecation warning when only FormBase.__dropdown_field_names__ is
set.
I can't think of a nice way to also use FormBase.__dropdown_field_names__ as a
property to throw deprecation warnings when getting or setting the
attribute...
Any ideas, anyone?

--HG--
branch : rename_dropdown_field_names_attribute
Make __possible_field_name_defaults__ an attribute on ConfigBase

which is the closest thing to a "core" global definition that we currently
have and it it fits quite good in there.

--HG--
branch : rename_dropdown_field_names_attribute
Merge that useless branch, sorry for the noise