change mouse cursor when over a selection

Change mouse cursor to a pointer when hovered over a selection
Revert "change mouse cursor when over a selection"

This reverts commit b5a1aaebbac57d145d47e3d4dc74e96b39bb0443.
change mouse cursor when over selection

moved to mouse handler. don't change when dragging or selecting.
selection hover improvements

fix issue with wrapped lines and compute only when necessary.
fix mouse not always changing on first line
Highlight matching HTML tag

fixes #1308
matching tag fixes

remove global editor ref, add listener
fix tag flicker

fix tag highlight flicker when selecting
use setCursorStyle instead of modifying classes
do not change mouse over selection if dragging isn't enabled
add todo reminder