wireshark: make enums global instead of local

These were exceeding the limit of 200 locals.
Merge into master from pull request #314:
wireshark: make enums global instead of local (https://github.com/floodlight/loxigen/pull/314)
pyloxi: reduce boilerplate code required for each module

All the important inheritance hierarchies are grouped together in python
modules like "of13.action". Previously creating a new module required 5 code
changes: the `modules` dictionary in lang_python.py, the `roots` dictionary in
codegen.py, a new `generate_*` function in codegen.py, and imports in the
init.py and module.py templates.

The new code gets rid of the `targets` dictionary left over from very old
loxigen. It uses the result of build_ofclasses to determine the set of modules
for a particular openflow version. The only code change required to create a
new module is defining its inheritance root in the `roots` dictionary.
openflow_input: add new TLV
Merge into master from pull request #317:
openflow_input: add new TLV (https://github.com/floodlight/loxigen/pull/317)
openflow_input: add TLVs for SFLOW gentables
fix header keyword bugs
Merge into master from pull request #318:
openflow_input: add TLVs for SFLOW gentables (https://github.com/floodlight/loxigen/pull/318)
pyloxi: generate subdirectory from version name
Merge into master from pull request #316:
pyloxi: reduce boilerplate code required for each module (https://github.com/floodlight/loxigen/pull/316)
Adding an oxm for mpls BoS indicator bit
Adding a boolean java type for the mpls BoS indicator bit
Cosmetic changes
wireshark: support OF 1.3 OXMs

Need to call the OF 1.4 match dissector instead of the 1.3 dissector.
Merge into master from pull request #320:
wireshark: support OF 1.3 OXMs (https://github.com/floodlight/loxigen/pull/320)
Merge into master from pull request #319:
Adding an oxm for mpls BoS indicator bit (https://github.com/floodlight/loxigen/pull/319)
Merge remote-tracking branch 'origin/master' into of14
openflow_input: add discriminator to of_table_feature_prop_experimenter

The standard-1.4 input files already contain this discriminator, so the IR
failed to unify.
Merge pull request #321 from rlane/of14

Merge master into of14 branch

The C and Java backends are currently broken.