Transaction size checking

[steinerkelvin]

• unallow too large transactions on mempool, returning errors on API call
• a command that outputs transaction sizes of the given statements, what fraction of a block size they would represent, showing warnings if they don't fit
  • this could be a feature of a more general check command that could also, in the future, outputs the minimum amount of blocks that would be needed

[steinerkelvin]

Example:

Size: 10 (1%)
Name: Available ✓
ctr {Leaf value}

Size: 80 (6%)
Name: Already Deployed ✓
fun (Gen depth)

Size: 40 (3%)
Name: Occupied XXX
fun (Sum tree)

Size: 40 (3%)
Run: fails XXX (?)
run {
  (Done (Sum (Gen #16)))
}

Size: 4000 (200%) Doesn't fit XXX
Name: Available ✓
fun (Fib act)

[racs4]

I think this can be closed due to the changes in #221