String.hh: removed useless semicolon after namespace closing bracket
Vec.hh: isFinite, hasNaN, hasInfinite: handle non-FP types more gracefully
Vec.hh: moved data members to top of class
Vec.hh: Vec<>::dot: fix type of `missingValue` parameter
Vec.hh: Vec<>::operator==: handle non-FP types
Vec.hh: define typedefs _before_ we use them.  Missed in @edc0910.
Vec.hh: added constructor for converting from Vec of diff. value-type
Vec.hh: indented standalone multiplication operator properly
Vec.hh: added some missing headers
Vec.hh:  add std::is_array<spt::Vec<_N, _ValueType> > => true