Merge branch 'master' of https://github.com/j6t/gitk

Merge branch 'master' of https://github.com/j6t/gitk

* 'master' of https://github.com/j6t/gitk:
  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
  gitk: fix MacOS 10.14 "Mojave" crash on launch
  gitk: fix error when remote tracking branch is deleted