Revert "Do not return next block production time in the past"

This reverts commit 92886ed33570465abe1661ecba0318fa517ed0fd.
Revert "Fix underflow bug in delegate loop"

This reverts commit 592c1216afe994bb67cea3d11cf4fcf80a9cf3a8.
Implement "wallet_enable_delegate_block_production * <enable>"
Merge pull request #391 from vikramrajkumar/enable_all

Implement "wallet_enable_delegate_block_production * <enable>"