condenser get_state accounts compat

[roadscape]

Condenser relies on quite a few account fields, mostly for the logged in user. In other cases it needs only very basic details. However, the logged-in account plus all others which are needed for 'soft references' are kept in the same structure.

Since hive does not serve full account data (e.g. block-accurate keys/permissions as needed for login and transfers), we need to find a solution which will serve condenser without changing core hive requirements.

Potential solution:

• deliver all hive 'lite' accounts in a separate key
  • have condenser read there first for soft refs
  • benefit: lightweight hive-native responses, serves 95% of cases
• for the rest, ensure condenser always accesses accounts through a central method
  • e.g. using the existing getAccount method
  • which already has ability to re-fetch accounts not in accounts key

[roadscape]

action plan cc @bnchdrff @gl2748

stage 1

• do not serve any account data from hivemind
• verify that condenser is able to recover by requesting accounts as needed (e.g. ensure critical calls all use UserSaga/getAccount which knows to fetch if missing)

stage 2

• have hive serve lightweight account data under a different key
• light accounts are used (exclusively?) by condenser's discussion thread view. have condenser check for light account data w/ fallback to legacy.
  • will save us excess calls for data which can be served natively by hive.

[roadscape]

Issue w/ account tabs: the feed/blog/comments/replies tabs require account key to be present. For now testing omitting accounts on discussion threads only.

[roadscape]

This is now a condenser-focused issue: steemit/condenser#2899