Updated documentation, 'default' in getParameterDefinitions replaced by 'initial'

- documentation updated to include bool and longtext parameters
- 'default' in getParameterDefinitions() replaced by 'initial' (but
still supported for backwards compatibility). This is because default is
a javascript keyword
Path2D.appendPoint: points are implicitly converted to CSG.Vector2D
Path2D.appendPoints() method added
Support for 2D Bézier curves added (CSG.Path2D.appendBezier())
Added Vector2D.abs()
cube, roundedCube, rectangle, roundedRectangle can now be passed a corner1 and corner2 parameters instead of radius and center
Fix typos in error message
path2d.appendArc added, to draw arcs between two points
Support for larger models, fix zoom problems, increased zoom range
Now supports returning multiple objects from the main() function

A dropdown list will be shown after the jscad file has been rendered.
This allows to quickly switch between different objects without
re-rendering the jscad file.
See http://joostn.github.io/OpenJsCad/#renderingmultipleobjects
doc update
added a "more" option to hide advanced features by default, but still be able to use them
for parsing the parameters within openjscad the global parameter 'debug' is not available, so define it also in the function itself
Merge branch 'gh-pages' of ssh://github/joostn/OpenJsCad into gh-pages
Implemented support for 'initial' in getParameterDefinitions extended to all supported types.

- The varialbe named initial is assigned to the value of paramdef.initial if it's defined,
- otherwise paramdef["default'] is used.
- If both aren't defined, then the variable initial stays undefined.
The initial/default value is applied if the variable is NOT undefined (!== undefined)
Merge branch 'initial_for_all_types' into gh-pages
replaced 'default' by 'initial' in getParameterDefinitions