Improved Catalog handling

- Improved FrontendCommand.GetCanonicalUri()
- Extracted ICatalogManager from CatalogManager
- Created CatalogManagerExtensions
Added --no-fetch option for "0install add" and "0install integrate"
Updated ReSharper
Cetnral.WinForms: Tweaked AppTile and AppTileList
Updated NanoByte.Common
Use object output instead of string output for "0install list" and "0install list-feeds"
Changed "0install store list" to list stores instead of implementations

Added "0install store list-implementations" as a replacement
Added "0install search"