Database Cleanup

[danieljsummers]

There are a few fields in the database whose intent has changed, but the name has not. Prior to v2 RC, fix any such names, and take this opportunity to change data and support types' fields to be capitalized, per F# standard naming conventions.

(This will mostly affect the RethinkDB implementation, but ensure that the SQLite mappings also remain correct.)

[danieljsummers]

• Changed WebLog.themePath to WebLog.ThemeId, and changed it to a proper ThemeId (this led to some different handlers to render themed templates, and changes in the DotLiquid theme_asset filter)
• Changed Page.showInPageList to Page.IsInPageList
• Changed feedEnabled, categoryEnabled, and tagEnabled in RssOptions to IsFeedEnabled, IsCategoryEnabled, and IsTagEnabled
• Changed iTunesCategory and iTunesSubcategory in PodcastOptions to AppleCategory and AppleSubcategory (ITunesCategory looks like an interface type, not a concrete type)
• Changed PodcastOptions.guid to PodcastOptions.PodcastGuid
• Changed WebLogUser.userName to WebLogUser.Email
• Removed UploadDestinationConverter (FSharpLu's single-case DU converter can handle it)
• Pushed these name changes throughout the view models that use them
• Modified RethinkDB implementation to use nameof for fields it addresses rather than strings
• Added conversions for RethinkDB tables that will be needed when beta 5 is released (no conversion planned for SQLite; I do not believe there are any users yet)