Disable caching of chart vertical offset values

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Revert "Disable caching of chart vertical offset values"

Restore caching, in favour of a an actual fix.

This reverts commit da490eab8c8da28f659040838b7d32b0d51c76ac.
Purge cached chart vertical offsets on redrawAll

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Merge pull request #1016 from opf/feature/ui-component-table-widgets-merged-timeline-chart-group-expansion-fixes

Fix timeline chart redrawing when group element expansions are toggled