Add auto-height for textbox controls

This adds the possibility to have auto-sized textboxes. Works the same way as with labels. Additionally it's possible to also resize the corresponding pagecontrol together with the textbox with `<resizepagecontrol>true</resizepagecontrol>`.

Mainly it makes it possible to keep old designs in DialogYesNo, DialogOK etc. with the new textbox control instead of the old labels. 

One thing which I recognized is that there is a new line in the textbox in some dialogs, e.g. if you delete a source, it says

"

Are you sure?
"

instead of just

"
Are you sure?
"

in the DialogYesNo. Now there are two ways this could be fixed:

1. Change calls of `CGUIDialogYesNo::ShowAndGetInput(751, 0, 750, 0)` to `CGUIDialogYesNo::ShowAndGetInput(751, 750, 0, 0)` so there is no empty first line.

2. Always remove any whitespace from the text which is added to the textbox.

Which one is preferred?