Filter notice styling and panel adjustments

* Based on @clarkepaul's commit here:
https://github.com/silverstripe-droptables/sapphire/commit/e5de6c06489f3449ee8131bf4ee2a4e1b2380bee
* Kept margin adjustments, but avoided implementing tab changes, as tabs have chnaged a lot since original commit

Before:
![4_06_13_12_13_pm](https://f.cloud.github.com/assets/984753/602941/cb1a36c8-ccab-11e2-8394-b1ee68f7fdf0.png)

After:
![4_06_13_12_12_pm](https://f.cloud.github.com/assets/984753/602942/d0f47086-ccab-11e2-8302-c36479c804c6.png)

Connected to this pull request: https://github.com/silverstripe/silverstripe-cms/pull/764