Issue#61

The documentation .md file describing the config of all the beans is added to the 'doc' directory.

This PR contains all the code for the support of ranking the mfa methods (configured by the method e.g. [mfa_method1:1, other_mfa_method:2, yet_another_mfa_method:3] so the lower integer number means higher rank) and in the end the code would pick the highest one out of the ones available for any given mfa transaction - regardless of the definition source for the mfa request e.g. request param vs SP (registered service) vs principal attribute)