Remove the Bootstrap sketch

This sketch is now (again) moved to
libraries/pinoccio/examples/Bootstrap, since that makes it easier for
people to load it from the IDE.
Add build.sh script to build Bootstrap sketch

This build script will be used to build the official Bootstrap sketches.
It automatically detects the version number from git tags (but only if
the code used is identical to the tag, local modifications set the build
number to -1).
Add license header to update.sh and create-vm-img.sh