ellipsize overlong icon texts and add tooltips, bnc#879959

For the overlong text of icons in yast2-control-certer-gnome, ellipsize them and add mouse hovering tooltips.
Problem here is taht you also use 2 whitespace, but it is after if, so usual indentation looks like
```
if something
  action;
```
but your is 
```
if something
action;
```
which is hard to read and see that `return` is associated with `if`