* allow running more or fewer validators
* use deterministic key generation for tests to avoid exhausting system
RNG
* update README with simulator docs
* write the data of each validator to separate file, instead of a big
chainstart.json (makes it easier to run different validator counts)
* s/CrosslinkRecord/Crosslink/
* {MIN,MAX}_DEPOSIT to {MIN,MAX}_DEPOSIT_AMOUNT; rm SHARD_PERSISTENT_COMMITTEE_CHANGE_PERIOD; per https://github.com/ethereum/eth2.0-specs/issues/378 and 35adc9c61a rm persistent_committees, persistent_committee_reassignments, and ShardReassignmentRecord
* complete switchover from status/ValidatorStatusCodes to status_flags/INITIATED_EXIT/WITHDRAWABLE validator representation
You'll need the latest versions of nim-eth-p2p, nim-serialization
and nim-json-serialization.
Before starting the simulation script, make sure to delete any previous
json files from the simulation folder:
```
rm tests/simulation/*.json
tests/simulation/start.sh
```
This should survive the creation of few blocks before diying with a
block validation error.
* spec updates
* balances move out to separate seq
* bunch of placeholders for proof-of-custody / phase1
* fix inclusion distance adjustment
* modify state in-place in `updateState` (tests spent over 80% time
copying state! now it's down to 25-50)
* document several conditions and conversations
* some renames here and there to follow spec
Zahary Karadjov
Jacek Sieka
Dustin Brody
Mamy Ratsimbazafy
Jacek Sieka
Yuriy Glukhov