Point2D type does not work with IMPORT/EXPORT DATABASE

Steps to reproduce:

```
LOAD SPATIAL;
CREATE TABLE test (p POINT_2D);
INSERT INTO test (p) VALUES (ST_Point2d(0,0));
EXPORT DATABASE 'test';
DROP TABLE test;
IMPORT DATABASE 'test';
```

The final line produces the following error, and the data is not imported:

```
Conversion Error: CSV Error on Line: 2
Original Line: POINT (0 0)
Error when converting column "p". Could not convert string "POINT (0 0)" to 'POINT_2D'
```