- core#880

Add snap, global follow mode

bump sibyl, grpcbox deps to pull in fix for silencing invalid_preface error logging

add version to jsonrpc

add height dbus endpoint

Implement ability to query stats for a single validator.

add block age dbus endpoint

Implement hbbft_perf for JSONRPC.

JSON/RPC string fixes

Audit 75

Remove the "verbose" option from the ledger_validators call and make the
items it returns (nonce and name) part of the normal result set.

Update the `ledger_validators` call to:
* Return more JSON-native datatypes, especially integers and floats,
  where possible.
* Always include an `address` element
* Optionally include a `name` element and `nonce` element if
  the `verbose` parameter is set.

This output is slightly different than the previous version, which
would return the validator address in `validator_address`, and even
then, only if `verbose` had been set.

I believe that `address` is a critical identity property to the
validator, not an optional one. Human-readable angry-purple-tiger
name, on the other hand, is optional instead.

Fix the `ledger_validators` method so that the return type of the "name"
attribute for a validator appears properly in the JSON results as a
string instead of a list of integers.

Also add the validator's address to the result set, since that is
an important identifier to have.

Fixes helium/miner#908.

Fix several points in the JSON/RPC interface where items which
should be strings in JSON are instead appearing as lists of integers
in result sets.

Likewise, fix an issue in the opposite direction, for `get_account`,
where the account address wasn't being B58 decoded before being
handed off to the ledger for querying.

Remove the "verbose" option from the ledger_validators call and make the
items it returns (nonce and name) part of the normal result set.

Implement the `hbbft_perf` for JSON/RPC use, as requested in
helium/miner #873.

A large portion of this code originally lived entirely within
`miner_cli_hbbft.erl`, so rather than duplicate it, the essential
information gathering now happens in `miner_util.erl` (per Evan's
suggestion) and is then parsed and formatted in different ways
by the CLI (`miner_cli_hbbft.erl`) and the JSON/RPC handler
(`miner_jsronrpc_hbbft.erl`).

This is a cherry-pick commit to rescue a branch that has been
screwed up by a bad rebase/merge.

- core#917

- core#915

- core#914
- core#918

Start next round early if node does not have its proposal in

fix #893 - jsonrpc p2p_status jsx encoding error

Audit 74