breaking(lit-core):

removed:
- setCustomBootstrapUrls()

privatised:
- _handshakeWithNode
- _getRandomHexString
- _sendCommandToNode
- _getNodePromises
- _getSessionSigByUrl
- _handleNodePromises
- _throwNodeError

feature:
- Added `EPOCH_READY_FOR_LOCAL_DEV` as constant with JsDoc

Author: Ansonhkg