Implement BlockCache Trait #152

Job	Run time
Latest build on ubuntu-latest	6s
Build target wasm32-wasi	20s
Check ZFuture build on Linux	1m 48s
Bitrot check	1m 37s
Check ZFuture build on macOS	1m 57s
Clippy (MSRV)	33s
Check ZFuture build on Windows	3m 54s
Clippy (beta)	14s
Code coverage	3m 56s
Intra-doc links	2m 15s
Rustfmt	14s
protobuf consistency	1m 10s
UUID validity	6s
Test on Linux	1s
Latest build on windows-latest	10s
Test Orchard on Linux	1s
Latest build on macOS-latest	11s
Test NU6 on Linux	1s
Test on macOS	2m 5s
Test Orchard on macOS	2m 25s
Test on Windows	1s
Test Orchard on Windows	1s
Test NU6 on Windows	1s
	23m 7s

Provide feedback