Adding new cli endpoint --patch-from= (#1940)

Adding new cli endpoint --patch-from= (#1940)

* Adding new cli endpoint --diff-from=

* Appveyor conversion nit

* Using bool set trick instead of direct set

* Removing --diff-from and only leaving --diff-from=#

* Throwing error when both dictFileName vars are set

* Clean up syntax

* Renaming diff-from to patch-from

* Revering comma separated syntax clean up

* Updating playtests with patch-from

* Uncommenting accidentally commented

* Updating remaining docs and var names to be patch-from instead of diff-from

* Constifying

* Using existing log2 function and removing newly created one

* Argument order (moving prefs to end)

* Using comma separated syntax

* Moving to outside #ifndef