Remove reduntant whitespace from buttons

New lines in the code of add-action, add-project, dashboard, and hide-controls buttons are converted to redundant whitespace after the buttons (e.g. in page controls, or tiddler controls), making them stand apart from core buttons.

This commit adds \whitespace trim pragma to those buttons, so that no whitespaces are created after the icons.

For example, the buttons in page controls before this change (notice the selected spaces after GSD5 buttons, but none after the core buttons):

The same after the proposed changes:

I didn't add \whitespace trim to the other buttons (convert-action, delete-tiddler), because I didn't see any difference with it or without. It might be worth adding for consistency or potential different uses of the buttons though.