Limit query contract depth

[alpe]

Inspired by https://github.com/terra-money/core/pull/584

We want to prevent from recursive smart queries that consume a lot of resources but may not cost much fees.
Options we have:

a) allow level n depth of queries where each contract that runs a smart query increases the depth by 1.

example:  
  A(0) -calls-> B, B(1) -calls -> C(2) -calls->D 
  A(0) -calls-> B, A(0) -calls -> C(1) -calls->D

b) allow n number of total smart queries in total

example:  
  A(0) -calls-> B, B(1) -calls -> C(2) -calls->D 
  A(0) -calls-> B, A(1) -calls -> C(2) -calls->D

[ethanfrey]

This would be breaking. Best to do by 1.0 if you don't want to wait til 2.0, right?

Seems fine with me

[alpe]

Replaced by #670