* Add default peer limits configuration
If discovery is enabled for a given cluster - we will set a default
expected number of peers for each enabled service. For example:
- if cluster is rinkeby has a discovery enabled we will
check which services are enabled
- if whisper is enabled we will set min and max limits by default
- if les is enabled and infura is not used we will set limits too
When statusd is used - configuration must be provided using configuration
supported by statusd.
* Fix deadlock in les peer set
This change will greatly simplify writing unit tests when a node is required but data persistence is irrelevant.
I also Introduced some refactoring and unit tests for `StatusNode`.
- [x] [#797] : Remove unused methods PopulateStaticPeers, ReconnectStaticPeers, removeStaticPeers, removePeer
- [x] [#797] : Rename node.Manager to node. StatusNode and simplify its public api
- [x] [#797] : Rename all references to nodeManager to statusNode
