Make exporter descriptions translatable
Fix JSON deserialiser to allow all fields

Previously we were filtering to a small set of known fields (which was
implemented at the beginning of TW5 as part of the build process for
TW2).
Update alltiddlers.template.html to use new exporter
fr-FR translation of exporter file descriptions
Merge pull request #1080 from xcazin/frn

fr-FR translation of exporter file descriptions
More icon tweaks
Move page export button next to import
Improve styling of search buttons
Extend set variable widget to work with filters
Add tabbed table of contents
Tweak docs
Style tweak
Tweak home button icon