SQLiteScalarQueryable

##Overview SQLiteScalarQueryable exposes an interface for scalar (aggregate) queries.

####Count Returns the number of rows in the table associated with the model.
Executes on current thread and on background thread respectively.

static func count() throws -> Int
static func countInBackground(completion: (Int, SQLiteModelError?) -> Void)

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public protocol SQLiteScalarQueryable {
    static func count() throws -> Int
    static func countInBackground(completion: (Int, SQLiteModelError?) -> Void)
}