Master refactored

As a result of [extensive discussion](https://github.com/civicrm/civicrm-wordpress/issues/13), here's the existing plugin refactored such that existing functionality is preserved (with some fixes) but wrapped in a new architecture. Comments liberally applied in places where I think the plugin needs attention.

* All plugin text can be translated using WP-native methods.
* Fixes [admin context bug](http://issues.civicrm.org/jira/browse/CRM-12616?focusedCommentId=51167&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-51167)
* Adds useful hooks for Civi-related plugins
* Offers more structured development roadmap

For more info, please refer to discussion above.