Dependence on Oauth PECL extension removed

Following changes were made in this commit:
1. Dependence on PECL extension of Oauth is now removed by using the
oauthlib of moodle.
2. Restored the original version of Evernote Library as there is no
dependence on Oauth PECL Extension now. Initially, it needed some hacks
to get it work at all times.
3. Improved the coding style further.
4. Simpler inclusion of files.
5. Improved the directory structure.
6. Removed the hard coded strings at multiple places.
7. Removed the code where it was removing the style attribute of the
tags. (ENML supports style attributes which I was removing in the
earlier versions)
8. Removed the use of $_SESSION, $_GET and $_POST variables in the code.