show units of weight in inventory menu

subj.

was:
![was](https://f.cloud.github.com/assets/5421954/1787284/272a9a2c-6903-11e3-9372-2d150e28a50e.png)

is:
![is](https://f.cloud.github.com/assets/5421954/1787285/2d9c8622-6903-11e3-863c-e9b82be659e9.png)