CRTs: allow anyone to trigger closing revenue share

[mochet]

Problem

People start a revenue share, it ends but they never place the closing TX which means it is impossible for the CRT to return to the market.

Solution

Allow for the runtime to let any account trigger the close revenue share TX--there doesn't seem to be any malicious action possible with this and the DAO could set up an account that does it automatically up to some certain scale.