Add support for infoset dataType member

- Add new setIncludeDataType and getIncludeDataType functions to the
  InfosetOutputter API to configure if InfosetOutputters should include
  the dataType member when creating infosets. It is left up to specific
  InfosetOutputter implementations if an how to represent this member in
  their infosets
- The XMLTextInfosetOutputter and ScalaXMLInfosetOutputter are updated
  to include the xsi:type attribute when this is enabled. They also
  define the "xsi" namespace prefix if not already defined. Other
  InfosetOutputters do not currently implement this.
- Update the TDML Runner to enable this flag for all infoset outputters.
  The TDML Runner already supports type-aware comparisons when xsi:type
  is provided, so enabling this allows all TDML test to use type aware
  logic. This means expected infosets no longer need to include xsi:type
  when for type-aware comparisons.
- Add new "infosetIncludeDataType", which calls setIncludeDataType if
  set. This allows enabling this feature without needing to modify code
  to call the new API function
- Fix TDML tests that used an xsi:type value that did not match
  the actual value
- Discovered a bug where xs:decimal elements could be output with
  scientific notation. This is not legal in XSD so these elements are
  now output using .toPlainString

Deprecation/Compatibility

- Previous versions of Daffodil could sometimes use scientific notation
  when outputting elements with an xs:decimal type, which XSD does not
  allow. Daffodil now always outputs xs:deicmal types using standard
  decimal notation without any exponent part.

DAFFODIL-182