Full headers only because of templates
Some changes, start to deal a little bit better with Jeans
Adds MatrixCoeffType to AtmosphericMixture, it serves the
purposes of storing precalculations for mean free path
Changes in interface:
 - first guess is provided
 - boundary conditions are provided
 - cached values, so no more need of other concentrations and altitudes
Merge pull request #2 from SylvainPlessis/dev-try

Dev try