add Modelica mode

The two new files
   CodeMirror/mode/modelica/modelica.js
   CodeMirror/mode/modelica/index.html
add a new language mode.

The file modelica.js has been generated with Jison (see https://github.com/omuses/moijs). The Modelica mode uses the CodeMirror fold addon.

There are remaining lint messages about "Named function expression" and "Unused" in the automatically generated code. Please tell me if the code must be changed such that the messages disappear.