Will now display full stack values of weight/volume. Misc ui improvements.

* The 'same square!' popup can be ignored as it will pass the next
 keypress (except q and esc) and disappear.
* '0' for weight or volume will appear dimmed.
* current/max number of items displayed at top right
* current inventory total displayed above 'weight vol' header.
* [stack amount] moved to it's own column as it's easier to read.