Accept `enablePersonalization` boolean as a valid setting parameter

[aseure]

All API clients currently should accept the enablePersonalization boolean
as a valid search parameter, which defaults to false when missing. However,
@rayrutjes recently reported that this parameter is also part of the settings
of an index.

The needed change is to expose the enablePersonalization boolean as a
valid setting parameter, which defaults to false when missing. It still
needs to be accepted as a search parameter as well.