Constructor for fileHandler, more methods for DataPoint

Added a constructor for fileHandler class when given a file. Added some more private members & get/set methods to DataPoint.cs
Merge branch 'Sarah' of https://github.com/iontrapimperial/Spectroscopy into Sarah
Added list of dataPoint objects to fileHandler, with methods
New constructor for dataPoint

Construct instance given array of data & starting point (from within fileHandler only)
Additional methods in dataPoint class

Also set metadata for each dataPoint object when it is created within fileHandler