revision of code Air.mo and Water.mo: remove duplication of code, correct derivatives, use more consistently reference_T, ...
revert some of the changes, according to the suggestions of Micheal Wetter + implementation of non-constant heat conductivity for water + convertion of the polynomial for the density to use Kelvin instead of degC
add fixme with question: is the derivative of lambda necessary? + minor revision
revision of AirPTDecoupled.mo + minor revision of Air.mo
Merge pull request #36 from damienpicard/issue21_Media

Merge Damien's changes to issue21_media