Implemented plugin.create_port: fixed_ip and mac_address

Implemented create_port with fixed_ip attribute
Implemented tests for create_port with fixed_ip attribute
Implemented create_port with mac_address attribute
Test fixes on allocate_mac_address ipam tests
Implemented tests for create_port with mac_address attribute
Merge pull request #61 from asadoughi/create_port

Implemented plugin.create_port: fixed_ip and mac_address