Fix bootstrap.sh problems
Created by: DomThePorcupine
There were a lot of problems pointed out to me with the initial pull of this file. I think I have fixed them all,
- Fixed allowing for alternative package managers under Debian/Ubuntu
- Fixed assuming yes to installing packages, now user is prompted to agree
- Fixed blindly installing git, QEMU, Virtualbox, etc. these things are tested for and skipped over if installed
- Changed default emulator to QEMU
- Added ability to install QEMU on OSX
- Added comment advising
qemu_no_kvm
on OSX - Cleaned up other general things