Fix traps in main.sh:
 - Make sure we exit on interrupt
 - Make sure clean-up commands are not executed twice
Add addtrap function. Do not run exit 2 on EXIT trap.
Make sure chroot is completely copied on bootstrap.
Use settrap/addtrap in other parts of the code.
Merge branch 'croagh+trap' of git://github.com/drinkcat/chroagh into croagh

Improve trap handling.
Add undotrap function and clean up comments.