Basic JMicrodata implementation in com_content (single article view), also JMicrodata implementation in plugin Content - Vote

A basic implementation of JMicrodata library in the CMS , implemented the library in com_content (single article view) and in plugin Content - Vote.

#### Testing instructions (todo list)
##### Backend
1. Administration (backend panel) → System → Global Configuration (Site tab) → SEO Settings → 
_you should find a toggle button to enable/disable globally microdata semantics_

2. Administration (backend panel) → Content → Article Manager → Options (button) → Articles (tab) → _you should find a toggle button to enable/disable microdata semantics globally in com_content_

3. Administration (backend panel) → Content → Article Manager → Edit (edit any article) → Options (tab) → _you should find a toggle button to enable/disable microdata semantics in the current article, you should also find a dropdown list for choosing the microdata type_

##### Frontend
1. Please __make sure you have you have enabled microdata__ from the administration backend panel (from the previous step).  
2. You should have enabled the _Content - Vote plugin_.
3. Administration (backend panel) → Content → Article Manager → Edit (edit any article) → Options (tab) → Show Voting (dropdown list) → _select Show_
3. Live Site (frontend) → Single Article (single article view, article from previous step in which you've enabled microdata) → Open the page source code (in firefox ctrl+u) → you shuould see microdata semantics in the html code
4. Copy and paste the source in http://www.google.com/webmasters/tools/richsnippets

You should play around to see if everything works fine, if you have problems or difficulties in testing let me know, I will help you.

##### Small 'problems/questions'
1. Should be or not a global configuration toggle button to enable/disable microdata semantics?
2. In com_content, where should stay the enable/disable toggle button? in Options (tab)?

If this implementation works fine and the feedback is OK, I start with other PRs in order to finish the implementation of JMicrodata in com_content and other components/modules/plugins.
Thanks.