Improve 'ActiveHosts' behavior
First, I changed it so that 'ActiveHosts' sorts the hosts by preference. As we add more preferences like geography and reliability, the UI doesn't need to worry about price estimation as much.
Second, I extended the /renter/hosts/active
call to support limiting the number of hosts returned to 'numhosts'. This field is optional, and has testing.
I think, in another PR, we should add a field that just gives a price estimate, instead of having the UI do the price estimate. The renter knows a lot better what it's behavior is going to be.