allow Lua to connect an arbitrary method to a property signal
change format of flavour-text translation keys

This is so that when the keys are sorted alphanumerically, all the text
for a particular flavour is grouped together.
sort translation keys alphanumerically in all en.json files
return a connection object that can be used to disconnect from the property
pass the property key and new value to Lua property signal handlers
auto-commit: translation updates
Merge remote-tracking branch 'johnbartholomew/reorder-flavour-translations'
auto-commit: translation updates
auto-commit: translation updates
auto-commit: translation updates
Merge remote-tracking branch 'robn/object-properties-lua-function'
documentation fix