prefixed action strings with 'router_' to namespace them.

I noticed the action constants are very generic strings (not namespaced like 'router_jump' etc.):
```
export const JUMP_ACTION = 'jump';
export const PUSH_ACTION = 'push';
export const REPLACE_ACTION = 'replace';
export const POP_ACTION2 = 'back';
export const POP_ACTION = 'BackAction';
export const REFRESH_ACTION = 'refresh';
export const RESET_ACTION = 'reset';
export const FOCUS_ACTION = 'focus';
```
As I understand Redux, all actions get passed to all reducers when you use `combineReducers`. We see these strings as being so generic that it opens a very real risk of me (or another module I did not read) dispatching an action that evaluates to the same string, triggering an action that was not supposed to be triggered. To prevent this I propose the following change, or any other that diminishes this risk.

Prefix actions in Actions.js for namespacing