Define function to group m/z values based on expected differences

[jorainer]

Impement a (fast) function to group m/z values in an input vector based on their differences. This could be a core function to be used in isotope detection or adduct grouping in a m/z vector.

Before implementing we should check:

• could we re-use something from MsCoreUtils?
• check the C functions from xcms - could be that there is already such a function implemented.