es_objects plugin fixes

[oxarbitrage]

while writing documentation to the plugin: https://github.com/oxarbitrage/worker-proposals/blob/master/es_objects.md

i found 3 points that need attention and fixes:

• [x] Balance tracking, change to account_balance.
• [ ] Limit order tracking, when the limit order is created and filled in the same block the original limit order will not be saved. Generally, if an object is updated and then deleted in a block, data in ES is not updated (if we don't delete it).
• [ ] Feed tracking, several feeds coming in the same second.

ill take care of them.

[cedar-book]

Related links (2019-03)

• https://dev.bitshares.works/en/master/supports_dev/elastic_search_plugin.html#elasticsearch-plugin
• https://dev.bitshares.works/en/master/bts_guide/tutorials/index.html#plugin

[oxarbitrage]

change in balance tracking was done here https://github.com/bitshares/bitshares-core/pull/1271

[oxarbitrage]

I think this issue should remain open even if https://github.com/bitshares/bitshares-core/pull/1271 was merged. The reason is that not all the items in the issue were addressed by the pull. I am moving this to the next milestone.

[abitmore]

Moved to next milestone.