Add test for OrderedDict subclass as NDData.meta
Fix the meta tests
Make Table.meta and NDData.meta behave the same
Use same tests for Table and NDData meta
Use descriptor for ``meta`` attribute on Table, NDData, Column, and MaskedColumn
Removed unused code
Minor fix
Setting ``meta`` to an empty dict is more explicit than clearing what is currently there.
Make sure that meta is tested on the classes in which it is used
Make sure that MetaData.__get__ works even if instance._meta is not defined
Merge pull request #1686 from astrofrog/uniform-meta-behavior

Uniformize Table and NDData meta behavior