Better checkpoint formats

[rubenhorn]

SimpleMD checkpoints are simple ASCII files:

<num particles> <dimensions>
<#1-value1> <#1-value2> ... <#1-value9>
<#2-value1> <#2-value2> ... <#2-value9>
...

Checkpoints could be enhanced with additional (human-readable) meta-data about the simulation scenario:

• domain size
• domain offset
• density
• boundary condition
• etc.?

[rubenhorn]

A simple solution would be to introduce bash-style comments. (Everything after # is ignored when loading a checkpoint.)