Rework gettransaction / getblock RPC calls

This PULL reworks new (post-0.6.*) features of the
gettransaction/getblock RPC calls as follows:

It removes the 'decompositions' object argument from getblock,
replacing it just a list of transaction hashes; equivalent
(I believe) of passing the {"tx":"hash"} decomposition.

It replaces the 'decompositions' object argument of
gettransaction with a boolean flag; if true, returns
the same stuff that the {"script":"obj"} decomposition
would return (txins/txouts as hex, disassembled, and bitcoin
addresses).

It adds a "rawtx" field to the output of gettransaction,
that is the entire transaction serialized and hex-encoded.

It removes the "size" field from gettransaction, since the size
is trivial to compute from the "rawtx" field (either take the
length after hex-decoding, or just compute it as hex-length/2).