Allow the creation of exclusion limits with SFramework

CLs limits are used by a number of different analyses. It would be nice if there was an action and calculator to allow for this to be done with SFramework. There should be a few steps involved:

1. Create action to calculate exclusions limits.
2. Create LimitCalculator to perform the above action.
3. Create a plotting action to draw the "Brazil-flag" type plots.
4. Create the function to actually nicely draw the above plots.