Cleanup desktop applets code

Pliant provides several desktop applets:

Files browser

Text editor

Document editor (word processor)

Schema editor

The main quality of these is that the code is very short, generally around 1000 lines, so could be easy to customize. On the other hand, I would describe the current implementation as first generation, so the code is not that clean and modular.
So, at some point, I'll have to rework them to turn them to good candidates for teaching purpose.

The document editor underlying storage also has to be change to enable to keep changes from hitting the disk (storage layer) until some flush is requested, so that if the same paragraph is modified again and again (repeat on backspace as an example) it wont fill the log with uninteresting informations.