Add option to insert completion item on PointerPressed/PointerReleased/DoubleTapped

[mgarstenauer]

This PR adds an options to choose whether completion items are inserted on PointerPressed, PointerReleased or DoubleTapped.

This is an improvement on #414 and addresses the feedback by @gebodal mentioned on issue #413.

In addition, this fixes an issue where first click in the CompletionWindow is swallowed by the PopupWithCustomPosition tooltip.