add API to Cursor to get column value type

    } data;

} __attribute__((packed)) field_slot_t;

#define FIELD_TYPE_NULL 0

#define FIELD_TYPE_INTEGER 1

#define FIELD_TYPE_FLOAT 2

#define FIELD_TYPE_STRING 3

#define FIELD_TYPE_BLOB 4

#define FIELD_TYPE_NULL 5

/**

 * This class stores a set of rows from a database in a buffer. The begining of the