Add Style configuration

The following functionalities are added to configure aerc ui styles.
- Read stylesets from file with very basic fnmatch wildcard matching
- Add default styleset
- Support different stylesets as part of UiConfig allowing contextual
  styles.
- Move widgets/ui elements to use the stylesets.
- Add configuration manual for the styleset

commands/util.go

@@ -32,7 +32,7 @@ func QuickTerm(aerc *widgets.Aerc, args []string, stdin io.Reader) (*widgets.Ter
 
 	term.OnClose = func(err error) {
 		if err != nil {
-			aerc.PushError(" " + err.Error())
+			aerc.PushError(" "+err.Error(), 10*time.Second)
 			// remove the tab on error, otherwise it gets stuck
 			aerc.RemoveTab(term)
 		} else {
@@ -56,7 +56,7 @@ func QuickTerm(aerc *widgets.Aerc, args []string, stdin io.Reader) (*widgets.Ter
 
 		err := <-status
 		if err != nil {
-			aerc.PushError(" " + err.Error())
+			aerc.PushError(" "+err.Error(), 10*time.Second)
 		}
 	}