[ADD] google_meeting module v.7.0

This PR contains the module **google_meeting** which provides a solution for synchronizing crm_meeting in Odoo v7.0 with Google Calendar.

I applied on the module https://github.com/solutions2use/google_api  developed by @solutions2use  a strong PEP8 cleanup and a bit of refactoring. I also renamed the module to google_meeting because it seemed more suitable.

See the description in the module manifest file for the installation notes.
How can I pass account to the global variable? Please, could you provide an example? Thank you in advance.