InfoBox extended, WindowChild content changes on coord change

- InfoWindow Content stays fresh by forcing doShow on coords change
- uiGmapInfoBox to add closeBoxDiv as pref over closeBoxUrl

Close box code via css div:
![screen shot 2014-12-16 at 12 08 28 am](https://cloud.githubusercontent.com/assets/583593/5448893/c0ad9f2a-84b7-11e4-8cab-dc6033ed2603.png)

vs: gross default
![screen shot 2014-12-16 at 12 09 04 am](https://cloud.githubusercontent.com/assets/583593/5448897/c86f3a84-84b7-11e4-9c2c-71712d7794ff.png)

@zacronos @aesnyder @cthrax 


An empty string is the original? (I'm assuming closeBoxUrl not being defined means not custom)