fix item description

- Modify displayed price according to PR #5960 - last two digits are cents (see snapshots below);
- Fix coverage value (see snapshots below);
- Fix some 'signed/unsigned comparison' warnings in item.cpp;
- Minor astyling of item.cpp.

Was:
![bad](https://f.cloud.github.com/assets/5421954/2240512/98e4be14-9c97-11e3-8fd7-dc626b898d62.png)

Is (price of the bra is modified for demonstration purpose):
![good](https://f.cloud.github.com/assets/5421954/2240513/9e54f6ca-9c97-11e3-87ef-d4b0af59de3d.png)