Fix body scroll issues when iOS keyboard pops up.

When, after clicking in the text, the iOS keyboard
pops up, the entire editor body is scrolled upwards
because the window is shrunk, even if there was
no way to scroll it before.
This means that the toolbar slides upwards and out
of the visible part of the viewport.

This is unacceptable, therefore this commit introduces
a fix:
CSS-translate the toolbar when detecting a scroll. focusout,
or touchmove event.
Overlay the eventTrap outside and over the cursor.

This commit pulls the event trap outside the cursor,
and as a child of the canvas,
and makes the Caret track the cursor's position and
position the trap above the cursor.

This means that there is no need to manually
blur and focus the eventManager whenever an
operation is executed.
Do not set focus in a timeout on iOS.

When attempting click-to-move, in most desktop
browsers we need to get the new selection in a
simple 0-timeout, because the window selection
is not immediately updated when handling the
mouseup event. The focus to the event trap is
set after this is ready. Otherwise, clicking
within a selection will not do anything.

Unfortunately, in iOS Safari, it is impossible
to set focus within a timeout. Therefore, this
commit takes the least painful and simplest
thing route: check navigator.platform for
iPad, iPod, and iPhone (the hope is that this
will be reliable because of Apple's consistency),
and in that case avoid computing the selection
and focus assignment within a timeout.
Stop using a contenteditable and use an input.
Apply body-scroll correction to caret/eventTrap positioning
and to SvgSelectionView.
Disable scroll-on-focus for the eventTrap
whenever the iOS keyboard is open.