Personas: add 6 default themes

Change-Id: Id8a920054c5b6f560ff2b26ce39c2a99574ad680
Reviewed-on: https://gerrit.libreoffice.org/60929
Tested-by: Jenkins
Reviewed-by: andreas_kainz <kainz.a@gmail.com>

cui/source/options/personalization.hxx

@@ -20,7 +20,7 @@
 
 #define CATEGORYCOUNT 6         // Number of persona categories
 #define MAX_RESULTS 9           // Maximum number of search results
-#define MAX_DEFAULT_PERSONAS 3  // Maximum number of default personas
+#define MAX_DEFAULT_PERSONAS 6  // Maximum number of default personas
 
 class FixedText;
 class FixedHyperlink;

extras/source/gallery/personas/personas_list.txt

+white/preview.png;white/header.png;white/footer.png;;#000000;#ffffff
+gray/preview.png;gray/header.png;gray/footer.png;;#000000;#ffffff
+dark/preview.png;dark/header.png;dark/footer.png;#ffffff;#000000
+pink/preview.png;pink/header.png;pink/footer.png;;#000000;#ffffff
+sand/preview.png;sand/header.png;sand/footer.png;;#000000;#ffffff
+green/preview.png;green/header.png;green/footer.png;;#000000;#ffffff