ensure tab stop for column hider trigger node
ensure tab stop for the ColumnHider trigger node and allow it to be displayed by pressing enter/space
Add keyboard nav controls

+ immediately focus first checkbox within the popup when it opens
+ allow ColumnHider popup to be dismissed by pressing escape
Add Dialog Role, Escape to close

+ Pressing Escape while the columnhider dialog is open will cauase it to
close
+ focus returns to the dialog toggle button when the dialog is closed
+ Add dialog role to dialog div
Add aria-label and supporting i18n

Add aria-label to the ColumnHider popup dialog and supporting nls
files