Hints for kolourpaint in main

Hints

• asv-url-not-secure
  org.kde.kolourpaint.appdata.xml:399 - http://www.kolourpaint.org/
  Consider using a secure (HTTPS) URL for this web link.
• asv-unknown-tag
  org.kde.kolourpaint.appdata.xml:6 - developer
  Found invalid tag. Non-standard tags should be prefixed with `x-`. AppStream also provides the <custom/> tag to add arbitrary custom data to metainfo files. This tag is read by AppStream libraries and may be useful instead of defining new custom toplevel or `x-`-prefixed tags if you just want to add custom data to a metainfo file.