fix usage and check $PATH
bugfixes + code cleanup

- new functions:
    * bind_chroot()
    * unbind_chroot()
    * wait_for_device()
    * summarize_instance()
- mount /dev/pts in chroot (some programs need this).
- add cleanup function/trap for make_bootable_drive().
- don't umount chroot or delete loopbacks when NOCLEAN is set.
- added variable $base_part for `/dev/mapper/$(basename $base_loop)p1' path.
- wrapped commands and comments at 80 cols (hi mom!!!!).
- move pre_grub() call closer to actual GRUB work, pretty print, etc.
wrap at 80 cols
conditionally enable acpi hotplugging

this allows vnics to work better when attached to guests
invsblduck's plugin examples
Merge pull request #6 from invsblduck/master

Bug fixes and code cleanup/enhancements