Better support for physical units

Merge pull request #318 from DimitriPlotnikov/master

Improve CLI output printing unit warnings.

Bug fix: solve SLI documentation problem

Merge pull request #311 from DimitriPlotnikov/master

Bugfix: update CMake template to use the latest help generator

Improve NESTML's syntax.

Merge pull request #310 from DimitriPlotnikov/master

Renamings of language constructs and predefined functions.

Fix GSL code generation

Merge pull request #298 from DimitriPlotnikov/master

Prepare bugfix release.

Use new syntax to integrate odes

Merge pull request #296 from DimitriPlotnikov/master

Use integrate_odes instead of more complex version with explicit variables

Improved console output.

Merge pull request #294 from DimitriPlotnikov/master

Prepare release

Improved code generation for NEST

Merge pull request #281 from DimitriPlotnikov/master

Prepare new release

Stability and syntax improvments

Merge pull request #260 from DimitriPlotnikov/master

Update models which are used in the NESTML tutorial

Improved SI type system

Merge pull request #247 from DimitriPlotnikov/master

Enable more usefull appliaction of the ODE aliases

Stability and syntactical improvment

Merge pull request #216 from DimitriPlotnikov/master

Prepare release