Tests
some adjustments
Initial abstract about setSwitch() and addCase() in Xgrid
Xupload handles uploads
Some tests
Some fixtures
Xnav can sets a css class to elements whith children

... and Xnav::breadcrumbs() doesn't shows a separator when its first
argument is false
EasyImage::wartermark() now works fine with alpha PNG

- Some fixes in EasyImage::cropResizing()
- and braces added in ifs, foreaches and switches
Some changes in Response.php
Some comments in Xupload.php
Added class Math.php