Add last vote time in account object

[abitmore]

User Story
As a UI developer I want a "last vote time" field available in account object so that UI can use it to fight voter apathy: bitshares/bitshares-ui#1934 (comment).

IMHO, the time should be updated when a user changed her votes but not every time when she updated her account.

Impacts
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• API (the application programming interface)
• Build (the build process or something prior to compiled code)
• CLI (the command line wallet)
• Deployment (the deployment process after building such as Docker, Travis, etc.)
• DEX (the Decentralized EXchange, market engine, etc.)
• P2P (the peer-to-peer network for transaction/block propagation)
• Performance (system or user efficiency, etc.)
• Protocol (the blockchain logic, consensus, validation, etc.)
• Security (the security of system or user data, etc.)
• UX (the User Experience)
• Other (please add below)

Additional Context (optional)
Add any other context about your request here.

CORE TEAM TASK LIST

• Evaluate / Prioritize Feature Request
• Refine User Stories / Requirements
• Define Test Cases
• Design / Develop Solution
• Perform QA/Testing
• Update Documentation

[oxarbitrage]

I first started this as a change to be done in the account_evaluator.cpp. More specifically i added a new field last_vote_time to the stats and was updating the date at account_update_evaluator::verify_account_votes.

The problem with this is that date will not be updated if your proxy voted for you, so i am thinking now the changes haves to be done into db_maint.cpp at around https://github.com/bitshares/bitshares-core/blob/develop/libraries/chain/db_maint.cpp#L1120

Feedback is needed, thanks.

[pmconrad]

The problem with this is that date will not be updated if your proxy voted for you,

IMO the last_vote_time should be updated when either the user votes on his own (i. e. updates his votes), or when he updates his vote settings. If the UI wants to display the last vote change time of the users proxy, it can be looked up separately in the proxy's account stats.

[oxarbitrage]

closed by #1449