BTManager 1.99.4

Another alpha. There are still some memory problems under Windows, so I don't want to make it a beta, though most of the features are implemented.

What's new:

* Extensive documentation in the Web UI
* Dispatching of downloads in subdirectories of 'incoming' according to regular expressions
* (experimental!) run as service under Windows
* Progress bars are now in PNG, instead of BMP (using libgd). Increased portability and huge bandwidth savings.
* Bug fixes