Tracking Issue for Milestone 3

[scilio]

• [x] https://github.com/mimblewimble/mwixnet/issues/6
• [x] https://github.com/mimblewimble/mwixnet/issues/14
• [x] https://github.com/mimblewimble/mwixnet/issues/13
• [x] https://github.com/mimblewimble/mwixnet/issues/5
• [ ] https://github.com/mimblewimble/mwixnet/issues/4
• [ ] https://github.com/mimblewimble/mwixnet/issues/8
• [x] https://github.com/mimblewimble/mwixnet/issues/9
• [x] https://github.com/mimblewimble/mwixnet/issues/10
• [x] https://github.com/mimblewimble/mwixnet/issues/19