ui design reworked to look more similar to new mockup
- Added smiley.svg for smiley button
- Added smiley button (currently nonfunctional)
- (Re)added border radius for various widgets
- Added "DEBUG" define if CMAKE_BUILD_TYPE is debug
- (Re)added F5 theme refresh if build type is debug
- Added filetransfer.svg for filetransfer button (currently hidden)
- Updated Cellrenderer to get correct color for selected rows
- Removed Arrow button, moved all functionality to status button (for
  now)
- Made button_send_file visible on groupchats