VisList properties overidden upon `refresh_source` initialization about lux HOT 3 CLOSED

This issue also causes the string title property for Date to be overridden.

Fixing this issue should also resolve the Date issue.

from lux.

Now supporting a custom title override by avoiding unnecessary calls to enumerate_collection. Mark and channel override non-trivial since we need to extend determine_encoding channel assignment to work with the non-default, custom mark.

from lux.

Currently, we don't support mark override on Vis, since there can be conflicts with the input intent (e.g. user intent involves only a single quantitative attribute, but sets mark as scatterplot). We can revisit this once there are a better validator and parser that catches these issues. For now, _mark is set as private property.

from lux.