Put .sbtserver in .gitignore
Add how-to-run-terminal stuff to README.md
JLineReader: Move choice of ExecutionContext to where we have a basis

This EC shouldn't be passed in, because it's an implementation
detail (it isn't used to invoke code provided by the caller).
Log various JVM info to master.log on startup

The main thing that might aid debugging is the JVM options,
but went ahead and just dumped most of the stuff in the
runtime bean.
Merge pull request #181 from sbt/wip/havocp-misc

A few minor misc things