Added SQL Server Compact via Nuget
Renamed Timer.TagSet property to just Timer.Tags.
Made the report filter using <= instead of just <, so that it's inclusive.
Added SqlServerCeConfiguration class to specify the provider so that it's not required in an app.config.
Updated the Tag and TimerHistoryItem classes so that they have an id property for the primary key. These will be EF Code First entities.
Added initial database storage code. This uses Entity Framework 6 Code First with SQL Server CE. Added the standard IDataContext / DataContext, and also a repository class called TimerHistoryItemRepository. This now saves the current history items, and loads the history items from today into the database. Note that the reporting code will have to lazy load items before today if the user selects past dates in the date filter (this hasn't yet been done though). I've also added the MockDbSet library via Nuget so that the tests can pass in a mocked DataContext.