These are good to have for backwards compatibility, but discouraged for new
development (default-taking functions should be used instead). The reason
is that the exceptions must be explicitly handled and may initially work but
then fail at an inopportune moment.
Mark the similar Java functions as deprecated as well for the same reason.
Update all the docs for consistency.
Mark overridden functions as such in both C++ and Java.
Make IsPersistent and GetFlags const in C++.
This enables listeners to be notified of not only value updates, but also flag
changes and deletions by using a bitmask to specify what notifications are
desired. The old API (which only provided a new/not new) flag is still
supported. This also subsumes the feature to listen to local changes (that's
one of the bitmask options).
The default behavior is to only notify remote changes, but for some
applications (e.g. GUI's) it's advantageous to know about local
changes as well.
This is (slightly) optimized in that local changes only result in
additional resources being consumed if (any) local listeners have been
created.
This matches the implementation provided by Java NetworkTable, with the
exception that the subtable is not provided (because it's not a value).
The listener still can get access to the subtable by calling
source->getSubTable(key).
