Make :q only close the active window

Closes #4061
Fixes #1089

doc/changelog.asciidoc

@@ -27,6 +27,10 @@ Added
 Changed
 ~~~~~~~
 
+- `:q` now closes current window instead of quitting qutebrowser completely
+  (`:close`), while `:qa` quits (`:quit`). The behavior of `:wq` remains
+  unchanged (`:quit --save`), as closing a window while saving the session
+  doesn't make sense.
 - Completion highlighting is now done differently (using QSyntaxHighlither),
   which should fix some highlighting corner-cases.
 - The `QtColor` config type now also understands colors like `rgb(...)`.

doc/help/settings.asciidoc

@@ -294,9 +294,11 @@ Type: <<types,Dict>>
 
 Default: 
 
-- +pass:[q]+: +pass:[quit]+
+- +pass:[q]+: +pass:[close]+
+- +pass:[qa]+: +pass:[quit]+
 - +pass:[w]+: +pass:[session-save]+
 - +pass:[wq]+: +pass:[quit --save]+
+- +pass:[wqa]+: +pass:[quit --save]+
 
 [[auto_save.interval]]
 === auto_save.interval

qutebrowser/config/configdata.yml

@@ -3,8 +3,10 @@
 aliases:
   default:
     w: session-save
-    q: quit
+    q: close
+    qa: quit
     wq: quit --save
+    wqa: quit --save
   type:
     name: Dict
     keytype: