Cleanup type symbol usage by consolidating to manage in one spot. This makes them easier to use as well by providing a single rollup of all the common type symbol's used throughout core.
BREAKING CHANGE:
AndroidTransitionType is now a static member of the Transition class.
BEFORE:
```
import { AndroidTransitionType } from '@nativescript/core/ui/transition';
```
AFTER:
```
import { Transition } from '@nativescript/core';
Transition.AndroidTransitionType.enter; // etc.
```
