Plugin .desktop syntax

[wiiznokes]

This PR migrate the plugin conifg file from ron to .desktop. This allow to translate some metadata, like Name and Description.

Here is an example of the syntax

[Plugin]
Name=Calculator with unit conversion (uses Qalculate! expressions)
Name[fr]=Calculatrice avec conversion d'unités (utilise les Qalculate! expressions)
Description=Syntax: = <expression>\nExample: = 10 J / (196x^2) = 4 kW/s
Exec=calc
Icon=x-office-spreadsheet
Regex=^[=\\-0-9|(-0-9)].*
GenericQuery==\s
Priority=High
IsolateWith="^(=).*"

Maybe Plugin could be replaced by Desktop Entry, and Description by Comment, but i don't really see a value in this.

And update in fde was necessary and should be merged first pop-os/freedesktop-desktop-entry#37