ENH: dictionary checking methods with predicates on the input values

- can be used to check the validity of input values.

Example:

    dict.getCheck<label>("nIters", greaterOp1<label>(0));
    dict.getCheck<scalar>("relax", scalarMinMax::zero_one());

- use 'get' prefix for more regular dictionary methods.
  Eg, getOrDefault() as alternative to lookupOrDefault()

- additional ops for convenient construction of predicates

ENH: make dictionary writeOptionalEntries integer

- allow triggering of Fatal if default values are used

ENH: additional scalarRange static methods: ge0, gt0, zero_one

- use GREAT instead of VGREAT for internal placeholders

- additional MinMax static methods: gt, le