#370
#371

configurable http client user-agent string

fix building on jammy

no functional changes
just vte deprecated a function so needs a change to build on current

Fix the show/install action buttons on the desktop notifications

Update to match Ubuntu kernel site changed their main url

• change --save-config from being an option that you would have to apply to some command like list, to it's own command write-config
• remove --yes, yes-mode by default, since the auth prompt serves as a confirmation
• reorganize the startup sequence of events to avoid some duplicate actions and close some missed actions in some cases
• fix a few strings like some tooltips in settings were obsolete

• fix uninstall
• cli: distinguish commands from options by renaming all commands from "--command" to "command"

• support xfce4-terminal for external terminal
• fix bug failing to recognize installed mainline packages when the the mainline-ppa site replaces the packages you already have installed with newer ones with different datestamp in the version number
• sort list with flavors & rc versions better
• busy indicator mouse cursor & infobar
• localize more strings, and localize some existing ones more correctly (format specifiers instead of concatenation so that translators can reorder. format specifiers in place of quoted values that should not be translated)
• clean up the low verbosity console output a little
• new commandline flags - mostly to give cli access to some options previously only acessible from the gui
  --include-flavors / --exclude-flavors override the Hide Flavors config file setting
  --include-invalid / --exclude-invalid override the Hide Invalid config file setting
  --previous-majors # override the Previous Majors config file setting
  --include-all short for --include-rc --include-flavors --include-invalid --previous-majors all
--exclude-all short for --exclude-rc --exclude-flavors --exclude-invalid --previous-majors none
--lock / --unlock <list> lock or unlock the given list of kernels, same as the lock checkbox in the gui
  --no|--dry-run assume No for all prompts

Convert the settings dialog to a tabbed window to make the window small again so it fits on any screen.