Release 1.8.0 of bmv2

• ability to chose gRPC server address for simple_switch_grpc
• extra logging (with source info) when evaluating conditions and calling action primitives
• support for calling actions directly from control
• now using gcc6 in regressions instead of gcc5 (in addition to gcc4.8); we want to support gcc4.8 -> gcc6; we no longer run regressions with clang3.6 but we still do with clang3.8
• thrift RPC to clear all entries in a table: bm_mt_clear_entries
• verify checksums at the end of parsing and log an error message if checksum is not correct
• add ability to print supported bmv2 JSON version with --json-version command line option
• check that JSON version is supported in P4Objects when loading the JSON input
• gRPC requirement to use simple_switch_grpc is now 1.3.0
• removed the OverwritingHeader parser error, which is no longer part of the P4_16 spec
• add support for conditional jumps in actions, which enables us to support conditions in action bodies (P4_16) directly
• more advanced support for CRCs, with a list of predefined algos and the ability to specify your own polynomials in the JSON input
• support for P4_14 saturating fields
• thrift RPC to query the (JSON) id of an object by name: bm_get_id_from_name
• stub implementation of gNMI handler in simple_switch_grpc
• packet IO support in simple_switch_grpc