improving the MEH initial guess (after seeing some jobs crash due to bad initial guesses)
generic CIBlock<DataType, StringType> to be reused in FCI. RASBlock<DataType> = CIBlock<DataType, RASString>.

Note that std::is_base_of<CIString_base,StringType>::value is asserted.
Merge branch 'master' of https://github.com/shiozaki/BAGEL