Adding important graph metrics in pgRouting

[sbdtu5498]

Changes proposed in this pull request:

• These functions are based on my work in the past.
• I have added two more signatures based entirely on the previously implemented functions.
• Would be adding tests and documentation soon.
• Reviews and suggestions would be appreciated.

@pgRouting/admins

[robe2]

1. The functions have to be added as separate pull requests. Looks like you have at least 3 in here so need at least 3 pull requests
2. Documentation is not complete
3. All tests should pass
4. You need more tests, but I think you are working on that.

[robe2]

I'm going to close this one out since it needs to be split into more pull requests.

[sbdtu5498]

@robe2 sure. I will break it down and will put it in 5 different PRs for

• pgr_vertexBetweennessCentrality
• pgr_edgeBetweennessCentrality
• pgr_ithBandwidth
• pgr_bandwidth
• pgr_centralPointDominance