Refactored obj.go to a more generic approach
Added object support for already implemented expressions
Added test for limit object
Fixes https://github.com/google/nftables/issues/253
Fixes https://github.com/google/nftables/issues/113
Log expression implementation changed to better support different log options
Added uint16 support to the binaryutil package
Changed old log expression tests that were failing after change
Added a new test to check the implementation for multiple log options