- previously introduced `getOrDefault` as a dictionary _get_ method,
now complete the transition and use it everywhere instead of
`lookupOrDefault`. This avoids mixed usage of the two methods that
are identical in behaviour, makes for shorter names, and promotes
the distinction between "lookup" access (ie, return a token stream,
locate and return an entry) and "get" access (ie, the above with
conversion to concrete types such as scalar, label etc).
- Since 'bool' and 'Switch' use the _identical_ input mechanism
(ie, both accept true/false, on/off, yes/no, none, 1/0), the main
reason to prefer one or the other is the output.
The output for Switch is as text (eg, "true"), whereas for bool
it is label (0 or 1). If the output is required for a dictionary,
Switch may be appropriate. If the output is not required, or is only
used for Pstream exchange, bool can be more appropriate.
