add generic stylesheet for mobile phones

One of the things I noticed here in the US is that the use of smart phones is much more common than in the rest of the world (well, at least as in Germany ;-).

PP is somewhat usable on these gadgets but at least the BlackBerry should be supported by an own stylesheet which is a lot simpler than the current stylesheet(s). For example the links to the different sections of a project (messages, tasks, etc.) or the project selection should be drop-down boxes rather than simple lists.

In this stylesheet the links to the Admin section can be skipped completely since this is not a daily task and it is very unlikely that there is time pressure to do some admin tasks when beeing without a PC.