Implement CreateOrUpdate on IDbProvider

[ChaseFlorell]

IDbProvider needs a CreateOrUpdate method so that we don't have to make multiple calls.

SQLIte will be simple

INSERT OR REPLACE INTO Employee (id, name, role) 
  VALUES (1, 'John Foo', 'CEO');

SQL Server will be a little trickier. We could "merge" if it's easy to do in the dialect, or we have to do it the old way with an if exists call.

# merge example
MERGE dbo.ClientData AS [Target] 
USING (SELECT 12345 AS clientId, 'Some' AS data) AS [Source] ON [Target].clientId = [Source].clientId 
WHEN MATCHED THEN UPDATE SET [Target].data = [Source].data, [Target].updatedDateUtc = GetUtcDate() 
WHEN NOT MATCHED THEN INSERT (clientId, data) VALUES ([Source].clientId, [Source].data);

# if exists examlpe
IF NOT EXISTS (SELECT * FROM dbo.Employee WHERE ID = @SomeID)
    INSERT INTO dbo.Employee(Col1, ..., ColN)
    VALUES(Val1, .., ValN)
ELSE
    UPDATE dbo.Employee
    SET Col1 = Val1, Col2 = Val2, ...., ColN = ValN
    WHERE ID = @SomeID

Methods to add to IDbProvider

void CreateOrUpdate<TModel>(TModel model, string identifierName = "Id") where TModel : class, new();
void CreateOrUpdate<TModel>(TModel model, Expression<Func<TModel, object>> identifier) where TModel : class, new();
void CreateOrUpdate<TModel>(TModel model, IDbMapper<TModel> dbMapper, string identifierName = "Id") where TModel : class, new();
void CreateOrUpdate<TModel>(TModel model, IDbMapper<TModel> dbMapper, Expression<Func<TModel, object>> identifier) where TModel : class, new();
Task CreateOrUpdateAsync<TModel>(TModel model, Expression<Func<TModel, object>> identifier) where TModel : class, new();
Task CreateOrUpdateAsync<TModel>(TModel model, string identifierName = "Id") where TModel : class, new();
Task CreateOrUpdateAsync<TModel>(TModel model, IDbMapper<TModel> dbMapper, string identifierName = "Id") where TModel : class, new();
Task CreateOrUpdateAsync<TModel>(TModel model, IDbMapper<TModel> dbMapper, Expression<Func<TModel, object>> identifier) where TModel : class, new();