Improved alignment of the "ps" popup table

Push comment:

"Add and implement functions "pad_cell" and "align_table" to provide better alignment of the "ps" command popup table."

Now all the columns of the table 'ps' outputs, which gets displayed via a Naughty notification, have much better alignment and a cleaner look.

![popup-1366x768](https://cloud.githubusercontent.com/assets/9487006/5323094/948bdb28-7cc4-11e4-9f07-1a77fe871dce.png)