Numerous changes/additions to build out the SDK

* Renamed project and assembly from ENSDK to EvernoteSDK.
* Properly handle case where user cancels out of OAuth.
* Fixed a few bugs in the HTML -> ENML conversion process.
* Explicitly load all dependent assemblies in the sample apps.
* CS samples - some updates; added comments.
* New VBA (Excel) sample.
* Added a Nuget package for easy installation of the necessary
assemblies.
* Added a Setup project for easy COM registration of the SDK (required
for VBA usage).