Mouseenter event to keep painting

[nofurtherinformation]

If you are painting, move your cursor off of the map or map layers, then return, while still clicked, the map does not continue to paint as you would expect

[raphaellaude]

Fixed by #182, no @nofurtherinformation ?

[nofurtherinformation]

This is slightly subtly the opposite problem -- there are some cases where the application is too quick to cut off a paint event