rfc: unify maketx run and maketx call

[thehowl]

#1001

The summary of how I think we should be going:

• qeval and msg_call should have the same basic input: an expression which may return a value which is evaluated. With qeval, this is just a query and cannot modify state, while msg_call creates a tx.
• msg_call can, additionally, be enriched with some extra code, which is parsed as a normal Gno file.
  • This code is executed in the "realm" of the user; any contract calls from that code will have PrevRealm == OrigCaller.
  • msg_call's main parameter may call the functions defined in this realm. Ie. --address my_address --expr 'main()' will be essentially the way that maketx run is working now.