Make Npgsql use SSLStream for ssl connections instead of using Mono.Security.

Mono.Security assembly is used by Npgsql to provide ssl support.
SSLStream class found in .Net class library also provides support for ssl.
Before this patch, Npgsql used Mono.Security by default.
With this change, it will use SSLStream class found in .Net class library.
Merge pull request #275 from franciscojunior/change-default-to-SSLStream

Make Npgsql use SSLStream for ssl connections instead of using Mono.Security
Remove unused Web files
Add doxyfile for doc generation

Fixed #285
Add doxygen outputdir to .gitignore
Tweaks to doxygen
Unit test to reproduce #179
Fix CommandBuilder event registration

CommandBuilder wasn't properly registering to its DataAdapter
events, resulting in bug #179