Make layer/block hashes clearer

[lrettig]

Right now the explorer includes a "Hash" field for a layer:

And it also lists a layer's blocks by ID:

Separately, the API (v1) returns the "state root" (RootStateHash) and the "layer hash/mesh hash" (Hash) as of a given layer:

https://github.com/spacemeshos/go-spacemesh/blob/a2cdfd384c418189a0443e9c647a2e201c879701/api/grpcserver/mesh_service.go#L313-L329

Can we please confirm which of these values the explorer is showing for a given layer, and make this explicit? Can the explorer show both values for a layer? We should probably add tooltips explaining what these values are and how they're calculated.

Can we also allow the explorer to drill down into a block and display that block's data (transactions, in order) and metadata (including block hash)?