MIPField updates and field name pattern matching.

Major changes:
  MIPField is no longer noncopyable (unnecessary restriction).
  Implemented MIPInterp, which performs filtered lookups.
  Added PatternMatch.{h,cpp}, containing functions for wildcard matching of field name/attributes.

Minor changes:
  Added virtual Field::mappingChanged().
  Added MIPField::levelLoaded(), MIPField::getVsMIPCoord().