Interface improvements

[ES-Alexander]

• [x] added alternate constructors from_serial and from_udp that combine instance creation and connection
• [x] added __enter__ and __exit__ methods to allow using in a context manager (initialize on entry, close connection on exit)
• [ ] change each device to only care about its relevant messages
  • [x] changed global message definitions to integer enums, for grouping and scoping access
  • [ ] change parser to parse using input message set
  • [ ] define device-specific message sets
• [ ] add examples/simplePing360Example.py
• [ ] add tools/ping360-simulation.py script
• [ ] fix #57
• [ ] fix #60
• [ ] fix #88, fix #99
• [ ] fix #89
• [ ] fix #90
• [ ] fix #119
• [ ] fix #125
• [ ] fix #122
• [ ] fix #141
• [ ] rebase setup.py update to the end