Input validation for new filters, in UI and core/filters. Use newer Angular

app.js
 - Now depend on AngularJS 1.3.0-rc.1 or higher, due to it using
   getterSetter in ngModel (it's probably available in an slightly older
   1.3.0-beta version too)
 - As a bonus to upgrading, there is a minor, but visible performance boost
 - Input validation for new filters from the settings modal

filters.js
 - Type checks the properties of filters passed into `update()`
 - Refactor and add sugar

both
 - Better property names in filter model
 - Names are consistent throughout
 - The two models aren't exactly the same, the only difference being
   core/filters filters have an extra "channel_id" property