Attempt at adding lighting to heavy model. Does not work yet.
Don't report same-thread calling exceptions in pause()
Remove pronterface-related integration in printcore
Integrate host commands in pronsole and pronterface (#428)

Any host command (other than pause) will now be run as a pronsole
command. This will allow doing things such as #428 easily.
Correctly handle interrupts in pronsole upload
Add prepare_command helper to utils
Use prepare_command in pronterface slicing
Reorder pronsole into sections of functions