Implement freezer database (#508)

* Implement freezer database for state vectors

* Improve BeaconState safe accessors

And fix a bug in the compact committees accessor.

* Banish dodgy type bounds back to gRPC

* Clean up

* Switch to exclusive end points in chunked vec

* Cleaning up and start of tests

* Randao fix, more tests

* Fix unsightly hack

* Resolve test FIXMEs

* Config file support

* More clean-ups, migrator beginnings

* Finish migrator, integrate into BeaconChain

* Fixups

* Fix store tests

* Fix BeaconChain tests

* Fix LMD GHOST tests

* Address review comments, delete 'static bounds

* Cargo format

* Address review comments

* Fix LMD ghost tests

* Update to spec v0.9.0

* Update to v0.9.1

* Bump spec tags for v0.9.1

* Formatting, fix CI failures

* Resolve accidental KeyPair merge conflict

* Document new BeaconState functions

* Fix incorrect cache drops in `advance_caches`

* Update fork choice for v0.9.1

* Clean up some FIXMEs

* Fix a few docs/logs

* Update for new builder paradigm, spec changes

* Freezer DB integration into BeaconNode

* Cleaning up

* This works, clean it up

* Cleanups

* Fix and improve store tests

* Refine store test

* Delete unused beacon_chain_builder.rs

* Fix CLI

* Store state at split slot in hot database

* Make fork choice lookup fast again

* Store freezer DB split slot in the database

* Handle potential div by 0 in chunked_vector

* Exclude committee caches from freezer DB

* Remove FIXME about long-running test

beacon_node/store/src/errors.rs

@@ -1,8 +1,15 @@
+use crate::chunked_vector::ChunkError;
+use crate::hot_cold_store::HotColdDbError;
 use ssz::DecodeError;
+use types::BeaconStateError;
 
 #[derive(Debug, PartialEq)]
 pub enum Error {
     SszDecodeError(DecodeError),
+    VectorChunkError(ChunkError),
+    BeaconStateError(BeaconStateError),
+    PartialBeaconStateError,
+    HotColdDbError(HotColdDbError),
     DBError { message: String },
 }
 
@@ -12,6 +19,24 @@ impl From<DecodeError> for Error {
     }
 }
 
+impl From<ChunkError> for Error {
+    fn from(e: ChunkError) -> Error {
+        Error::VectorChunkError(e)
+    }
+}
+
+impl From<HotColdDbError> for Error {
+    fn from(e: HotColdDbError) -> Error {
+        Error::HotColdDbError(e)
+    }
+}
+
+impl From<BeaconStateError> for Error {
+    fn from(e: BeaconStateError) -> Error {
+        Error::BeaconStateError(e)
+    }
+}
+
 impl From<DBError> for Error {
     fn from(e: DBError) -> Error {
         Error::DBError { message: e.message }