Merge branch 'ml/themes'

Merge branch 'ml/themes'

* ml/themes:
  gitk: set minimum size on configuration dialog
  gitk: separate code blocks for configuration dialog
  gitk: make configuration dialog resizing useful
  gitk: add theme selection to color configuration page
  gitk: add proc run_themeloader
  gitk: eliminate unused ui color variables
  gitk: eliminate Interface color option from gui
  gitk: use text labels for next/prev search buttons
  gitk: use text labels for commit ID buttons
  gitk: do not invoke tk_setPalette
  gitk: use config variables to define and load a theme
  gitk: make sha1but a ttk::button
  gitk: use themed spinboxes

Signed-off-by: Johannes Sixt <j6t@kdbg.org>