Implement "new-style" name_firstupdate operations.

After a planned hardfork, allow name_firstupdate operations to take
place without a preceding name_new.  In this case, no hash/rand value is
present, and no checks are done for this.  This will allow simpler name
registrations in the future, at the loss of protection against "name
stealing" -- which seems no big deal in Huntercoin anyway.
Add RPC call for new-style registration.

The new RPC command 'name_register' performs new-style name
registration.  Also fix a problem with mining these.
Use AllowNewStyleRegistration in RPC code.
Merge pull request #86 from domob1812/name-new

Simpler "one step" name registration
Remove unused argument fLimitFree for AcceptToMemoryPool.

Always enforce limiting of free transactions.
Remove network fee from the code.

It was never used and will never be used, so just clean everything up.
Namecoin is being rebased anyway (without the net fee), so there's not
even a need to keep it to stay in sync with Namecoin.