[V134-specific] Slash points instead of bond slash for HandleDoubleSign

[V134-specific]

Intended to close #1691 (closed)
'Instant-ban validators on double-sign'
by incrementing slash points (withholding rewards) upon double-sign
rather than bond slashing 900,000 RUNE in 6 minutes.

("900,000 RUNE in 6 minutes":
MinimumBondInRune in Mimir is 30000000000000 (1e8 terms) which is 300,000 RUNE;
5% of the minimum bond per block means 20 blocks for the minimum bond;
900,000 RUNE is then bond-slashed in 60 blocks;
at 6 seconds per block (note Constants BlocksPerYear 5256000))
there are 10 blocks per minute, 60 blocks being 6 minutes.)