Convert block manager block handler to pure FIFO.

Rather than having a separate query channel for the block manager, use the
same channel so the block handler acts as a pure FIFO queue.  This
prevents possible starvation of query related messages.

ok @owainga
Fix some comment typos.
Update install command to also install utilities.

This commit updates the install command under the Installation section in
README.md to include all subdirectories thereby including the utilities
such as addblock and btcctl.
Updated getinfo to return new RelayFee and use btcjson.InfoResult
Improve non-standard tx error message.

This commit removes the word "only" from the non-standard transaction
error message when the number of items on the stack does not match the
number of expected items.

This was suggested by @mbelshe.
Change rate limit debug messages to trace level.
Reject orphan transactions from sendrawtransaction.

This commit modifies the sendrawtransaction RPC to reject transactions
which are orphans.  This mirrors the behavior of the reference
implementation.
Improve error return from sendrawtransaction.

Rather than simply returning "TX rejected" to the RPC client which
submitted a sendrawtransaction that fails, include the reason the it
failed.