Change @class docs tag to @classdesc
Add classdesc to gjslint custom tags
Add @classdesc to classes
Merge pull request #2178 from probins/classdesc

Use @classdesc notation.
Add @todo API and describe ol.geom.Geometry funcs

The `clone()`, `getSimplifiedGeometry()` and `getType()` methods are all
base class methods documented in subclasses.  They should appear in
ol.geom.Geometry in the API docs as well.