refactor(*): move FreshWidget code from freshdesk module into separate module

There are now three modules:
* freshdesk: contains wrapping code to manage common settings for both functional modules
* freskdesk-widget: contains the code for adding FreshWidget
* freshdesk-chat: contains the code for add FreshChat
docs(api): add API documentation
chore(grunt): add more build automation

* tasks for updating docs, releases
* task for updating GitHub pages branch
* update dev dependencies
style(ng): add vendor prefix to module names
docs(api): update documentation to reflect changes in module naming