Make English the source language of the interface text

Every tr() source string in the code and the forms is now the English
text, and French is a translation (qet_fr.ts) like the other languages.
Generated, not hand-edited: master ef795a21e5 converted by
qet-en-source (harness 4c4ddc9).

3144 messages get an English source, 665 already had one, 0 left French; 8 shared-wording pairs disambiguated.
C++: 2904 literals in 233 files. Forms: 809 strings in 65 files. All 34 .ts files re-keyed; qet_fr.ts filled.
lupdate check: PASS. What each of 38 languages shows, old vs new: same 118266, English instead of French 38433, comment fallback 51, differences 0.

sources/autoNum/ui/formulaautonumberingw.ui

@@ -38,7 +38,7 @@
       </sizepolicy>
      </property>
      <property name="title">
-      <string>Dénomination automatique :</string>
+      <string>Automatic name :</string>
      </property>
      <layout class="QHBoxLayout" name="horizontalLayout">
       <item>
@@ -50,7 +50,7 @@
          </sizepolicy>
         </property>
         <property name="text">
-         <string>Formule</string>
+         <string>Formula</string>
         </property>
        </widget>
       </item>
@@ -102,9 +102,9 @@
  -%prefix: Default Element Prefix
  -%l: Element Line
  -%c: Element Column
- -%F: Folio Name
- -%f or %id: Folio ID
- -%total: Total of folios
+ -%F: Sheet Name
+ -%f or %id: Sheet ID
+ -%total: Total of sheets
 You can also assign any other titleblock variable 
 that you create. Text and number inputs are
  also available.</string>