Eliminate support for sdk's below 47

[faddat]

While working through the repository this evening, It's become pretty clear to me that we've a complexity issue: main is on 46, while integrate-47 is on 47.

In addition to this, there are some changes between the branches that may not be entirely related to changing the version of the cosmos-sdk.

I suggest that we add to the Readme.md a notice that this software is for sdk 47+, so that we can:

• reduce the amount of migration code
• work from a common codebase
• reduce the likelihood of issues by narrowing scope

[faddat]

We did not do this and it's excellent