general: add support for declaring enums as struct members

the enum types are resolved to the wiretypes for the benefit of c-loxi.
py_loxi: support/resolve enum members of structs
openflow_input: declare of_flowmod.flags as enum ofp_flow_mod_flags

others will follow
java_gen: support enum types, sets of enum types
loxi_ir: add convience method is_bitmask
test_data for java_gen(of13): use new API
add more supporting types
refactor openflow types
add openflow.types.Metadata
edit dependencies in pom
remove types.L2MulticastId
openflow_input: changed syntax for openflow input parsing of enums
add java to default targets
Merge into master from pull request #64:
Changed type of port list in features reply to be OFPortDesc (https://github.com/floodlight/loxigen/pull/64)
Merge into master from pull request #63:
Improve support for enum_types (https://github.com/floodlight/loxigen/pull/63)
Merge into master from pull request #65:
add more types in org.projectfloodlight.openflow.types (https://github.com/floodlight/loxigen/pull/65)
Added missing break in case statement