Pull server files from http-{mock,proxy} into their own blueprint

Fixes #2356
Adds changeOrigin flag to http-server proxy.

After some poking around in the ProxyServerAddon and adding back the `host` param as the third parameter in here:

    app.use(function(req, res) {
      return proxy.web(req, res);
    });

I started poking around in node-http-proxy and found some earlier issues related to the "Host" header. http-proxy does not seem to change the Host header for outgoing requests, so you have to flag `changeOrigin` to make this happen.

I added changeOrigin and this immediately fixes my bugs. So, I'm not sure if this is the correct implementation (perhaps this should be an option sent to the proxy via cmd line or a ./server proxy), but I figured I'd push it so you can see where I am at. Hope it helps.

References:

* [Use changeOrigin for proxyRequest](https://github.com/nodejitsu/node-http-proxy/commit/cee3e2f590058aa049b2f0b463e50e96272039f3)
* [Original host not being passed through](https://github.com/nodejitsu/node-http-proxy/issues/621)
* [Host header comments](https://github.com/nodejitsu/node-http-proxy/issues/150#issuecomment-2702793)
Add changelog entry for #2610
Merge pull request #2610 from jgwhite/separate-server-blueprint

Pull server files from http-{mock,proxy} into their own blueprint
fail better with watchman
better logs
spell check
switch debug to ui.writeLine
Adds error message and throws exception when someone passes a bad `options.type` to `app.import`
Merge pull request #2647 from mattmarcum/app-import-options-test

App.import should throw exception when someone passes a bad type
Merge pull request #2645 from calvinmetcalf/watch-detect

fail better with watchman
Doesn't parse proxy url
Test that proxying to subdomains uses the right host.
Merge pull request #2615 from typeoneerror/ember-cli-http-proxy-2596

Adds changeOrigin flag to http-server proxy.
Add #2615 to CHANGELOG.
make application instances not use Pascal case
Trim trailing whitespace
The generated meta tag is now self closing
Merge pull request #2661 from xymbol/trim-whitespace

Trim trailing whitespace
Trim trailing whitespace