Added MimeEntity.Load() methods that load from a System.Net.WebResponse

Potential fix for issue #26
Moved the sqlite3.dll back to lib
Moved MimeEntity.Register() to ParserOptions.RegisterMimeType()
Cleaned up ParserOptions a bit
Merge pull request #27 from hultqvist/master

MimePart/Entity constructor with content type.
Minor cleanup to previous commit
Replaced MimeEntity.Load(WebResponse) with MimeEntity.Load(ContentType,Stream)

This patch better reflects what is needed in issue #26
updated docs
Bumped version to 0.19.0.0
Adding public MailboxAddress parser.