* fix stack overflow crash in REST/debug/getStateV2
* introduce `ForkyXxx` for generic type matching of `Xxx` across
branches (SomeHashedBeaconState -> ForkyHashedBeaconState et al) -
`Some` is already used for other types of type classes
* consolidate function naming in BeaconChainDB, use some generics
* import `forks.nim` from other spec modules and move `Forked*` helpers
around to resolve circular imports
* remove `ForkedBeaconState`, use `ForkedHashedBeaconState` throughout
(less data shuffling between the types)
* fix several cases of states being stored on stack in tests, causing
random failures on some platforms
* remove reading json support from ncli - this should be ported to the
rest json reading instead (doesn't currently work because stack sizes)
This refactoring puts the JSON-RPC and REST APIs on more equal footing
by renaming and moving things around, creating a separation between
client and server, and documenting what they are - the aim is to have a
simple-to-use base to start from when developing API clients, as well as
make it easier to navigate the code when looking for the legacy JSON-RPC
interface vs the new REST API.
* move REST client, serialization and supporting types to spec/eth2_apis
* REST stuff now starts with `rest_`, JSON-RPC stuff starts with `rpc_`,
more or less
* simplify imports such that there's a simple module to import for both
server and client
* map REST type and proc names to yaml spec more closely - in
particular, reuse operation and type names in `rest_types` to make
comparisons against spec more easy
* cleaner separation between client and server modules - modules common
between server and client such as `rest_types` and serialization move to
the spec folder - this allows the client to be built with less knowledge
about server internals
Jacek Sieka
Eugene Kabanov