Asset Permissions

Ian and I have come up with some enhancements to how security settings are stored. Wanted to document our conversation today and get going with it tomorrow:

1. Remove the need to save permissions into /media. This causes problems with replication in a cluster
2. Add viewgroups viewusers fields to Asset
3. Add Role based libraries. This is a list of libraries a Role has access to. Libraries are a flat list. Roles can picked from a list of libraries
4. Add a library editor for assets. All assets will be in the "default" library by default. These will use a check box interface
5. Add the ability to filter searches dynamically by Role values
6. Add system wide adminviewgroups to settings searcher (cached in AssetSecurityArchive)

We will need to migrate old permissions to the data dir with XmlFileSearcher