merge
Add st_ringbuffer function
Add missing st_ringbuffer function registration
Fix header
Merge pull request #241 from ebocher/ringBuffer

 Ringbuffer function #241 
Add the ST_RingBuffer function.

The signature is :

```mysql
SELECT ST_RingBuffer('POINT(10 10)'::GEOMETRY, 10, 3)

```

returns a multipolygon with 3 rings buffer. The distance between each rings is 10 meters.
Remove the extra call to ST_Graph (#240)

I was calling it an extra time when I created the cormen graph, but I
don't need the cormen graph for the st_graph tests!
Merge pull request #246 from agouge/240

Remove the extra call to ST_Graph (#240)

This explains the extra call to `ST_Graph` in #240 ... it's my stupid mistake.

I was calling it an extra time when I created the cormen graph, but I
don't need the cormen graph for the `ST_Graph` tests!
Use connection URL for columnlist detection
Move util method to TableFunctionUtil class
Add private constructor
Add author
Rename method
Merge pull request #247 from agouge/228

Move column list detection to utility class