- added support for free-hand re-definition of AoI based on the previous generated Shapefiles
 - implemented flow from index 1 on the method combo box (and forbid all the other ones)
 - created page with re-definition of AoI
 - moved createExtent and clip methods inside the layer class; refactored them for higher abstaction
 - created reclip method
 - added reclip layers (and constant strings) to the layer manager

- reviewed titles and sub-titles of pages
- refactored indexes to cope with the non-linear structure;
 - page indexes are set with an interval of ten, so we can insert new pages between them without refactoring the whole thing
 - now virtual nextID() *always* has to be reimplemented, on the page class (otherwise, how do we know where to go next?)

- refactored "broken" update progress bar function:
 - now the total is calculated in the beginning, based only in the first digit pages (branches don't count)