fix in xml writing wrt. undefined temperature tag
implementation and check of xml IO
fixes and tests for orthotropic parameter xml IO
added some more pressure units
added critical temperature parameter
added critical pressure parameter
added critical temperature and pressure properties
added method to convert from any unit to the current unit
added method that allows to add a value with unit
added critical temperature and pressure to default gaseous material
added boiling point property
cosmetics
fix in xml IO
fix in xml IO
fix in XML IO
Merge branch 'XMLmaterialIO'