Change to font sizes across the application

[JanBan]

There was a complaint from IWRD about the fonts (mainly on buttons) being too small.

This issue is about increasing the sizes a bit, without distorting the UI of the application. In most cases we still have some wiggle room, the main screen being a good example

If possible, it may be beneficial to make some "font size" const somewhere, at least for the buttons. Perhaps values/dimens.xml would be a good place?

The outcome of this issue will be validated later, on a meeting with IWRD.