Merge pull request #3652 from riadvice/accessibility-improve

bigbluebutton-client/locale/en_US/bbbResources.properties

bigbluebutton-client/src/BigBlueButtonMainContainer.mxml

...ebutton-client/src/org/bigbluebutton/core/KeyboardUtil.as

...client/src/org/bigbluebutton/main/events/ShortcutEvent.as

...lient/src/org/bigbluebutton/main/model/ShortcutOptions.as

...on-client/src/org/bigbluebutton/main/views/BBBDataGrid.as

...-client/src/org/bigbluebutton/main/views/MainToolbar.mxml

.../src/org/bigbluebutton/main/views/ShortcutHelpWindow.mxml

...rg/bigbluebutton/modules/caption/views/CaptionWindow.mxml

...ent/src/org/bigbluebutton/modules/chat/views/ChatBox.mxml

.../src/org/bigbluebutton/modules/chat/views/ChatWindow.mxml

.../org/bigbluebutton/modules/layout/views/LayoutsCombo.mxml

...uebutton/modules/present/ui/views/PresentationWindow.mxml

...screenshare/view/components/ScreensharePublishWindow.mxml

...es/screenshare/view/components/ScreenshareViewWindow.mxml

...igbluebutton/modules/users/views/RoomActionsRenderer.mxml

...rc/org/bigbluebutton/modules/users/views/UsersWindow.mxml

.../org/bigbluebutton/modules/videoconf/views/VideoDock.mxml