refactor(ngBind): name link and compile functions

For easier debugging.
refactor($compile): remove safeAddClass

This helper function does try/catch in case the element is an SVG element. jqLite does handle this properly (because it uses `setAttribute`. jQuery does not handle this and so we need to make sure we use `jqLiteAddClass` function.
docs(debugInfo): add docs for $compileProvider.debugInfoEnabled()