Approximating melting temperatures from freezing points inaccurate

[MadsR]

Melting temperatures measured from freezing points were too inaccurate.

For accurate melting temperature, an inverse system test is needed.

• Can go higher temperature gradient than usual 1 K/min
• Passive heating from turned off system might be sufficient
• Might need slight cooling during heating to slow heating process

[MadsR]

See #12