First commit of Class

First commit of class that compares a data histogram to a stack of histograms coming from simulation.
First commit of basic histograms

First commit of basic histograms that inherit directly from ROOT histograms. By using this approach we can add functionality.
Renaming files to pass to namespace paradigm.
Renaming file to change to namespace paradigm.
Renaming files to change to namespace paradigm.
Renaming files to change to namespace paradigm.
Renaming files to use new namespace 'rat'

Following decision to move from namespace 'at' to 'rat' this files had to be renammed and content changed accordingly.
Major changes to accomodate move to 'rat' namespace

* Removed 'IC' prefix from filename to be
* Renamed all classes and methods
* Fixed all call to classes to now use this namespace
* Minor bug fixes
* Added basic documentation
* Removed un-necessary comments
Renaming file to accomodate to new 'rat' namespace
Moving merging Plots package into Histograms package

Some of this tools belong on the Histograms package