Remove the import trello card feature

See the following discussion for rationale:

  https://github.com/wekan/wekan/issues/113#issuecomment-163039089

client/components/lists/listHeader.jade

@@ -23,7 +23,6 @@ template(name="listActionPopup")
       li: a.js-select-cards {{_ 'list-select-cards'}}
   hr
   ul.pop-over-list
-    li: a.js-import-card {{_ 'import-card'}}
     li: a.js-close-list {{_ 'archive-list'}}
 
 template(name="boardLists")

client/components/lists/listHeader.js

@@ -33,7 +33,6 @@ Template.listActionPopup.events({
     MultiSelection.add(cardIds);
     Popup.close();
   },
-  'click .js-import-card': Popup.open('listImportCard'),
   'click .js-close-list'(evt) {
     evt.preventDefault();
     this.archive();

i18n/fr.i18n.json

@@ -158,8 +158,6 @@
     "import": "Import",
     "import-board": "import from Trello",
     "import-board-trello-instruction": "In your Trello board, go to 'Menu', then 'More', 'Print and Export', 'Export JSON', and copy the resulting text",
-    "import-card": "Import a Trello card",
-    "import-card-trello-instruction": "Go to a Trello card, select 'Share and more...' then 'Export JSON' and copy the resulting text",
     "import-json-placeholder": "Paste your valid JSON data here",
     "import-members-map": "Your imported board has some members. Please map the members you want to import to Wekan users",
     "import-show-user-mapping": "Review members mapping",
@@ -182,7 +180,6 @@
     "list-move-cards": "Déplacer les cartes de cette liste",
     "list-select-cards": "Sélectionner les cartes de cette liste",
     "listActionPopup-title": "Liste des actions",
-    "listImportCardPopup-title": "Import a Trello card",
     "lists": "Listes",
     "log-out": "Déconnexion",
     "loginPopup-title": "Connexion",
@@ -257,4 +254,4 @@
     "view-it": "Le voir",
     "warn-list-archived": "Attention : cette carte est dans une liste archivée",
     "what-to-do": "Que voulez-vous faire ?"
-}
+}