Equality tests for dumpreader and SingleSpeciesAnalyzer

[skuschel]

Implement Equality tests for dumpreader and SingleSpeciesAnalyzer. This allows that ParticleAnalyzer can be added together without adding Particles twice, in case they overlap. It will also allow to easily check if a particle analyzer contains particles of another.

[skuschel]

Equality tests for dumpreader have been implemented 341cdae. Its not straigt forward what == should mean for singlespecies or multispecies objects including the option, that the particle lists might be reduced due to compression functions (like taking only particles with gamma > 2 or similar). Concept needed.

[skuschel]

Regarding #117 it may be useful to define "dr1 == dr2" to be True if they are returning the same particles in the same order (although from a possibly different dump)?

[skuschel]

If it becomes necessary to implement equality tests for singlespecies or multispecies objects, we can still do it. There is no obvious way here and also no obvious benefit. Closing the issue.