Fixed columns in with native scrollbars
internal feature: new option `debug = true|false` shows WalkontableDebugOverlay (makes it easier to debug issues with native scroll)
add missing semicolon
hide WalkontableDebugOverlay while mousemove (to allow clicking and scrolling what's underneath)
reuse original columnStrategy/rowStrategy in clones
set debug to false by default
fix vertical clone positioning in window mode
minimize number of callback calls in WalkontableScrollbars; fix vertical clone positioning
use the actual number of columns in colWidths
rename WalkontableScrollbarNative to WalkontableOverlay
remove unused properties and methods
get rid of lint warning
rename WalkontableScrollbarNative to WalkontableOverlay (2 places ommited by unintentionally)
two Walkontable tests were failing after a recent change [reuse original columnStrategy/rowStrategy in clones]
fix misleading name of a method