Initial support for PRACK
Preliminary 100rel support

It is supposed to be finished, except for SDP media handling.
It is not thoroughly tested.
Use a single timeout for dialogs

Don't use the old 64*T1 timeout for all states but confirmed.
Doc updates
Minor updates
100rel fixes and test updates
Updating tests
Working with PRACK state, UAC
100rel fully working, tests passing
Testing Travis DNS error
Testing Travis errors
Testing Travis errors