* [#776] Enable ZIP 317 fees support
* Deprecate ZcashSdk.MINERS_FEE
* Replace MINERS_FEE with Proposal API in Demo app
* Changelog update
* Bump SDK to 2.0.8 to produce snapshot version
The backend now supports proposals that create multiple transactions.
It still does not generate such proposals itself, and we assert this
inside the now-deprecated APIs.