Change the board import layout from a popup to a full page

This commit also removes the “import a single Trello card” as we couldn’t figure
out some reasonable use case.

We also create a new publication on the server to provide the minimal user
profile informations required to display an avatar.

client/components/boards/boardHeader.jade

@@ -175,7 +175,7 @@ template(name="createBoardPopup")
     input.primary.wide(type="submit" value="{{_ 'create'}}")
     span.quiet
       | {{_ 'or'}}
-      a.js-import {{_ 'import-board'}}
+      a(href="{{pathFor 'import'}}") {{_ 'import-board'}}
 
 
 template(name="boardChangeTitlePopup")

client/components/boards/boardHeader.styl

@@ -1,2 +0,0 @@
-a.js-import
-  text-decoration underline