pyloxi: move OFType logic out of code and into a table

This is easier to understand, but results in duplication which will be fixed in
the next commit.

Support for arrays was removed because apparently we don't use them anymore.
pyloxi: add convenience code to generate most OFTypeData objects
pyloxi: move OFType interface functions to module level

This removes the need to replace the LOXI IR OFType object in members with our
own version. If/when the core OFType is upgraded to an inheritance hierachy we
won't need to duplicate it in pyloxi.