themes: use hintbox and header gradient option in theme settings

Color gradient feature was originally intended for use
inside theme settings and it's not really suitable  for
generally use as default in all themes at the moment, so it makes more
sense to have options in theme settings and let the user decide
to customize this, unless enough other gui parts can use this feature.

data/locale/deutsch.locale

@@ -299,6 +299,7 @@ colormenusetup.menuhead Titelleiste
 colorstatusbar.text Infobar
 colorthememenu.head Theme auswählen
 colorthememenu.head2 Themes laden
+colorthememenu.menu_hints Hinweisfenster
 colorthememenu.name Themename
 colorthememenu.neutrino_theme Neutrino Theme
 colorthememenu.question Aktuelles Theme beibehalten?

data/locale/english.locale

@@ -299,6 +299,7 @@ colormenusetup.menuhead Header
 colorstatusbar.text Infobar
 colorthememenu.head Select theme
 colorthememenu.head2 Load themes
+colorthememenu.menu_hints Hint box
 colorthememenu.name Theme name
 colorthememenu.neutrino_theme Neutrino Theme
 colorthememenu.question Use selected theme?

data/locale/nederlands.locale

@@ -294,6 +294,7 @@ colormenusetup.menuhead Menu kop
 colorstatusbar.text Infobalk 
 colorthememenu.head Selecteer thema
 colorthememenu.head2 Thema's laden
+colorthememenu.menu_hints Hint box
 colorthememenu.name Naam thema
 colorthememenu.neutrino_theme Neutrino Thema
 colorthememenu.question Geselecteerde thema gebruiken?

data/locale/slovak.locale

@@ -300,6 +300,7 @@ colormenusetup.menuhead Hlavička
 colorstatusbar.text Text stavového riadku
 colorthememenu.head Výber vzhľadu
 colorthememenu.head2 Nahraj vzhľad
+colorthememenu.menu_hints Tip Box
 colorthememenu.name Názov vzhľadu
 colorthememenu.neutrino_theme Neutrino
 colorthememenu.question Použiť vybraný vzhľad?