This pull requests replaces type check hint assertions with type casts,
library sanity check assertions with conditional console.assert statements
in debug mode, and runtime sanity checks with assertions that throw an
ol.AssertionError with an error code for lookup outside the library.
With this commit test files provide namespaces (using goog.provide). This fixes the issue reported by @bartvde where goog objects cannot be used in Jasmine "describe" functions. It also frees us from having to add script tags for the test files in test/ol.html.
