Fixes for yandex2.core Placemarks.

Proper names for `properties` and `options`, put everything where it belongs.
No need for `postoptions` now, pass both `properties` and `options` in ymaps.Placemark constructor.

Support predefined icons from http://api.yandex.ru/maps/doc/jsapi/2.x/ref/reference/option.presetStorage.xml.

Use wide icon by default to fit the label if the label (`this.labelText`) is longer than one symbol.

Add `this.labelText` as the balloon header to keep it visible when the ballon is opened.

Remove `hideIcon: false,` it never worked.