Fix logging in start_assignment()
Add Ambient Copyright notice
Make stdout_line_fragments dict instead of list

We are using pids as indices for stdout_line_fragments. These quickly
get too big for a list.
Under Windows, use full path for first process arg

Under POSIX, the first argument to a newly started process needs to be
the binary's basename, withour the path.

Under Windows, however,. trial and error has shown that executing
process like this will fail, at least when the command to be executed is
a batch file.
Register a new process in self.processes later

This reduces the chances of ending up with an entry in self.processes
that refers to a process that is not even running. Ideally, this should
be done as a callback of the started deferred for this process.
Remove an outdated comment
Don't send agent_time_offset = "auto" to master

"auto" is not actually a valid value for agent_time_offset.  The master
will reject the agent's announce in that case.
Merge pull request #122 from guidow/various_jobtype_rework_fixes

Various jobtype rework fixes