Documentation on using SFrame

• Adding new packages to SFrame

This is what packages could look like:

MyAnalysis
     |___SFrame
     |___Common
     |      |___NtupleVariables
     |      |___SelectionTools
     |      |___UzhUtilities
     |      |___LeptonEfficiency
     |      |___...
     |___External
     |      |___GoodRunsLists
     |      |___...
     |___ExoDiboson
     |    |___ExoDibosonCommonSelection
     |    |___WPrimeAnalysis
     |    |___...
     |___Ztautau
     |     |___TagNProbe
     |     |___...
     |___...