ipdb: fix if_master attribute
ipdb: dotkeys __delattr__() missed proxying: fixed
ipdb: IPDB() as a context manager
tests: drop to pdb on errors and failures
tests: new ipdb tests

 * IPDB as a CM
 * representations
 * dotkeys class testing
 * review transaction
 * rename interface
 * up/down interface
 * failed create() case
 * remove ports
 * create vlan