Fix bug in manual column move

Repro for this bug:

1. Enable manualColumnMove
2. Click on the move tab of a column, but don't drag it

Expected: column is not moved

Actual: column can be moved to an arbitrary location

If this is the first time that move-column has been invoked since the
table was initialized, the afterColumnMove callback is actually invoked
with a newIndex parameter of undefined or NaN.

The cause is that endCol is not initialized unless the move tab is
dragged into a different cell. The simple fix is to always initialize
endCol = startCol as soon as we start dragging.
Merge branch 'release/v0.9.17' into develop
cleanup CSS vendor prefixes (with autoprefixer - https://github.com/ai/autoprefixer)
bugfix: Can't edit cell that is outside of the viewport (#1035)
code readibility: rename wtTable.parent to wtTable.holder
remove flags that are long unused
bugfix: context-menu-layer is not removed from DOM after $.contextMenu destroy
move getColumnHeaderHeight/getRowHeaderHeight to separate methods
native scroll - more usable version (needs performance improvements)
native scroll - use same logic for breaking rendering as with dragdealer
performance fix - cache clientHeight
important performance fix - only determine autoColumnSize when some change happened
performance fix - for native scroll estimation is faster than measurement
row height cache should be preserverd until data is not changed; native scroll should use the cache to remember position for scrolled cells
fix editing in native scroll mode
properly calculate how many rows to render in native scroll mode
fix editing in native scroll mode
fix scrolling in native scroll mode
security brake too strict
change condition because one of WOT tests was failing