Merge and extend ApiSession.getLiveContract and ApiSession.getLiveJson

[3Nigma]

We have ApiSession methods to retrieve live instances of type Contract and Json, but there aren't any to retrieve LiveAccounts, LiveFiles, LiveTokens and LiveTopics. We need to support these as well.

We should do it by merging ApiSession.getLiveContract and ApiSession.getLiveJson into a single, overloaded, ApiSession.getLive method. One overload for each type of entity.

Its signature could be something like: ApiSession.getLive(LiveEntityType, args): Promise<-live-entity-> which would lead to the following 2 methods for the existing Json/Contract retrievals:

• ApiSession.getLive(LiveEntityType.Contract, id, abi = []): Promise<LiveContract>
• ApiSession.getLive(LiveEntityType.Json, id): Promise<LiveJson>