Hints for frescobaldi in main

Warnings

• asv-description-has-plaintext-url
  org.frescobaldi.Frescobaldi.metainfo.xml:160 - ul
  The description contains a web URL in plain text. This is not allowed, please use the <url/> tag instead to share links.
• asv-description-enum-item-invalid
  org.frescobaldi.Frescobaldi.metainfo.xml:219 - ul
  Enumerations must only have list items (<li/>) as children.
• asv-description-enum-item-invalid
  org.frescobaldi.Frescobaldi.metainfo.xml:180 - ul
  Enumerations must only have list items (<li/>) as children.
• translations-not-found
  Unable to add languages information, even though a translation tag was present in the MetaInfo file. Please check that its value is set correctly, and all locale files are placed in the right directories (e.g. /usr/share/locale/*/LC_MESSAGES/ for Gettext .mo files).