Fixes for manabar calculation & other

Reviewers: @jziebinski @msobczyk

• Fix manabar calculation resulted in displaying wrong values (M instead of K) on dashboard
• Fix precision not being displayed by humanize_votes_with_comma (eg. clive show witness) - was always rounded to integer
• Fix warning about lost precision in HivePowerDataRetrieval
• Expose and use wax calculate_witness_votes_hp
• Use iwax.calculate_hp_apr instead of own Clive implementation