Add melting step before crystallisation run

[gnikit]

When attempting to run a crystallisation run, the temperatures are very low which most likely results into the initial lattice not melting and staying in the solid phase. Add the option to either

1. Melt the crystal with a high initial Temperature and then quench it.
2. Start with positions and velocities of a previous melted run.

[gnikit]

I am not sure that this is needed anymore since the bug that was giving bocus results has now been fixed. I will test and update