Encode length and punctuation in key IDs

This is to ensure we don't end up using the same string for two
strings using the same words but different length and punctuation.

_plugins/weblate-source-file.rb

@@ -21,8 +21,11 @@ module Weblate
     def self.get(source_text)
       source_text.nil? or source_text.empty? ? source_text
                                              : source_text.strip[0..150]
-                                                          .gsub(/([^\w\d\s\!]|\n)/, '')
-                                                          .tr(' ', '_') << "_KEY"
+                                                          .gsub(/([^\w\d\s\.\?\!]|\n)/, '')
+                                                          .tr(' ', '_') 
+                                                          .tr('.', 'P')
+                                                          .tr('?', 'Q')
+                                                          .tr('!', 'E') << "_" << source_text.length.to_s << "_KEY"
     end
   end