Merge pull request #29 from DaveAckley/master

Boot sequence tweaks & misc
Bare version of ExternalConfig, a class for reading configuration files
Added tests for ExternalConfig, which don't currently assert.
Merge from pull request
fixed merge this-> problem
A ByteSink that sends output in two directions
A ByteSink that remembers the last N lines of output to it
A Panel that displays a LineTailByteSink
Fixes to OverflowableCharBufferByteSink
Test LineTailByteSink and OverflowableCharBufferByteSink
Add a logging panel (on 'l' -- moved heatmap to 'h')
Small cleanups.  Also log simulation dir name
Dim out logger border
Possibly fix DHS 'top edge asymmetry' issue?