The 'tx_cap' RPC function is only used at session-creation time. For
this reason, it was not listed in the "official" RPC interface in
'block_session.h'. However, this makes the interface more obscure than
it needs to be. So this patch promotes it to a regular RPC function.
Issue #3092
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082