Implement other CRDT types

[peterzeller]

• Counter
• Last-writer-wins Register (LWW-Register)
• Multi-value Register (MV-Register)
• enable-wins flag (EW-flag)
• disable-wins flag (DW-flag)
• Grow-only Set (G-Set)
• Add-wins Set (AW-Set / OR-Set)
• Remove-wins Set (RW-Set)
• Grow-only Map (G-Map)
• Remove-Resets Map (RR-Map)

[red17electro]

I & @dlnshaminda added Multi-value register to the develop branch.