[ALOY-1493] [Alloy] Alloy sql adapter db_file to be function

// app/models/mytable.js
exports.definition = {
    config: {
        columns: {},
        adapter: {
            type: "sql",
            collection_name: "mytable",
            db_file: function() {
                var myFile = Titanium.Filesystem.getFile(Titanium.Filesystem.applicationDataDirectory, 'file1.sql');
                return myFile.exists() ? myFile.nativePath : Titanium.Filesystem.applicationDataDirectory + 'file2.sql';
            },
            db_name: "projectsDB",
            idAttribute: "UserID",
            remoteBackup: false
        }
    }
};