Designer mode improvements part 2

Designer mode improvements part 2

- fix designer and scripting buttons overflowing outside the navbar
  on smaller screen sizes
- fix close, code and delete buttons in action attributes being only
  partially clickable because they are being overlayed by the navbar
- use the default font for the canvas action element
- center the text within the action element horizontally
- increase font size fo the text within the action elements
- support deleting actions

Issue-ID: CCSDK-4177
Change-Id: I399677e18335d64d0761ae6ddc651b058869a8ff
Signed-off-by: Fiete Ostkamp <fiete.ostkamp@telekom.de>