Add polyline tool to Swing UI

Similar to SwingPolygonTool, but uses a BezierFigure that is open rather
than closed and a GeneralPathOverlay instead of a PolygonOverlay.
Merge pull request #58 from bnanes/polyline

Add polyline tool to Swing UI
SystemInformation: improve class javadoc
Fix style of PolylineTool classes
check-headers.pl: add Benjamin Nanes to authors
Reduce the WebDAV uploader lock timeout from 30 to 10 minutes

As suggested by Curtis Rueden in

	https://github.com/imagej/imagej/issues/59#issuecomment-38705515

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
gitignore: ignore scripts directory

This directory is useful to put scripts for testing during development,
but we will never commit scripts here; any scripts we want to ship in
production will go in src/main/resources of the relevant component.