Make TableColumns case insensitive
Reorder C type declarations

Old Cython version has problems with names used in the file before
they are declared.
Fix setter for property .active_sequence

Do not raise an exception if no sequence was active, before using the
setter to activate one.

Also rename the property from .sequence.
Rename Table.get_all to Table.columns.freeze and return TfsTable
Add function libmadx.get_table_list
Always return 'at' relative to element entry
Put TfsTable (etc) in cpymad.types

To make the cpymad package more independent from the rest of pymad.
Merge branch 'isolate-cpymad' into active-sequence

Conflicts:
	src/cern/cpymad/madx.py
Remove package pymad.abc

Remove the common abstract base classes for both pymad implementations.
Remove pymad.io

Not used anywhere anymore