Restore hosted-time crate and rework API of native programs

[tomaka]

#506 removes the hosted-time crate because it was too complicated to update.

#506 in general makes writing native programs considerably more complex. Not because of changes in the API of native programs, but because of changes in the messaging system that native programs make use of.

As such, native programs should be adjusted to be easier to implement, or entirely reworked.
cc #452