* Move public functions up in rent.rs

* Added RentStatus

* Fix test name for consistency

Co-authored-by: Michael Müller <michi@parity.io>

* Mark rent functions as unstable

* Add unstable interfaces to README

* Fix doc typos

Co-authored-by: Andrew Jones <ascjones@gmail.com>

* Use DefaultNoBound

* Simplify calc_share(1)

* Don't output empty debug messages

* Make `seal_debug_message` unstable

Co-authored-by: Michael Müller <michi@parity.io>
Co-authored-by: Andrew Jones <ascjones@gmail.com>