Add ST_Graph Analysis

`ST_GraphAnalysis` calculates closeness and betweenness centrality for nodes,
as well as betweenness centrality for edges. Possible signatures:
```mysql
ST_GraphAnalysis('input_edges', 'o[ - eo]')
ST_GraphAnalysis('input_edges', 'o[ - eo]', 'w')
```

where
* `input_edges` = Edges table produced by `ST_Graph` from table `input`
* `o` = Global orientation (directed, reversed or undirected)
* `eo` = Edge orientation (1 = directed, -1 = reversed, 0 = undirected).
  Required if global orientation is directed or reversed.
* `w` = Name of column containing edge weights as doubles