Metadata v12/refCount size change + misc fixes, improvements#41

Merged

splix merged 6 commits intosplix:masterfrom

blockchain:master

Nov 18, 2020

Commits on Nov 12, 2020

Fix CompactBigIntWriter when the value starts with a zero byte
pablojorge
committed

Commits on Nov 13, 2020

Fix Era serialization in Extrinsic reader/writer and Signature payload
pablojorge
committed

Commits on Nov 14, 2020

Commits on Nov 18, 2020