Add "Developer Communities" To Development Page

* Adds links to the #bitcoin IRC channel, Bitcoin StackExchange, and BitcoinTalk Dev & Tech board to the development page.
    
* Links to that section of the page from the devel docs.

Screenshot:

![2014-10-03-210045_452x338_scrot](https://cloud.githubusercontent.com/assets/61096/4514350/679172ce-4b67-11e4-88f3-aa3d1fd16a34.png)

**BitcoinTalk Quality:** a concern was raised in https://github.com/bitcoin/bitcoin.org/pull/589#discussion_r18311326 about the quality of help on BitcoinTalk. I did a quick, highly-subjective and unscientific survey of the top ten displayed non-stickied posts on the dev & tech board, and the help I saw being provided ranged from adequate to great. Many of the replies I saw came from members of the community whose expertise I trust.

I don't dispute that the forum has trolls and scammers, but I'd recommend it to a friend who needed a place to ask questions.

@saivann If you see anything that can be improved in the translation template stuff (or anything else), please feel free to push directly to the branch.
@luke-jr @harding Thanks for your answers. In general providing these links is only useful so I'm all for it. I also think it's a good idea to keep them below "Documentation" and "Get involved", just so this page remains mostly focused on "developing Bitcoin" as opposed to "using Bitcoin as a developer".