Booleans are represented as Boolean.TRUE/FALSE internally.
However, SQL89 does not have a concept of boolean, only strings
and numbers. So these are normally mapped to strings like "Y", "N".
Which representation is determined in subclasses.
(The JDBC java docs are useless as always "getBoolean gets booleans...").
(The issue is with JDBC, not SimpleORM. And of course SFieldObject
can always be used if really needed.)
Shared routine for converting database representations to booleans so all boolean
implementations can be consistent and so boolean classes can be attached to existing
database columns
Converts from the users external representation to
the internal representation stored in SRecordInstance.
This is deliberately quite permissive, and should work even
if the external world is a bit inconsistent.