Add Block icon not centered on dashboard

[rick-c]

Habari version: 0.10
OS: Linux

Using Mozilla based browsers, the plus sign in the add block button on the dashboard is at the very bottom of the button.

Using Google Chrome, the plus sign is near the top of the button.

In neither case is it centered on the button.

[chrismeller]

Could someone check this in Chrome in Windows as well? @ringmaster Had reported a similar issue with the icons on hp.o.

[Konzertheld]

In Chrome under Linux, it's actually centered, but just horizontally and it looks worse because of the rounded borders. In Chrome under Windows, it looks more like the first picture above. Increasing the line height to 10 fixes vertical position under Linux.

[Konzertheld]

I think for #230 we should just get rid of this button.