Cleanups/Fixes/Improvments to annotate code.

Cleanups/Fixes/Improvments to annotate code.

For cclient, simply use Socket driver. Don't use IMAP extension that
requires manual patching of PHP source.
Add support for the METADATA-SERVER and ANNOTATEMORE2 extensions.
Get rid of 'nocapability' and 'annotatemore' options. This should all be
determined automatically by the driver code. The other options (maxsize,
depth) can be emulated in software based on which extension is available
(TODO for annotatemore code).
Need to define new publicly available methods in all drivers (e.g.
Cclient and Socket Pop3 drivers).