add "Brackets" to user agent string, and move remote debugging port to config.h

Fix for adobe/brackets#2213

Modifies the user agent string to include "Brackets" followed by a slash and the version number (e.g. Brackets/0.19.0.0). This follows the convention of version numbers in user agent strings.

It also removes any spaces present in the app name, so that it will work properly with Edge Code.

The user agent string now looks like:

```
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_2) AppleWebKit/537.1 (KHTML, like Gecko) Brackets/0.19.0.0 Safari/537.1
```

For bonus points, also moves the hard-coded remote debugging port to a #define in config.h. By having it in config.h, we can set separate ports for Brackets and Edge Code. This means that we can debug both of them at the same time without having to worry about which one we opened first.