Fixed issue where shortcodes were parsed when loading ToS fields in the form editor, resulting in the replaced shortcode content saving over the shortcode itself.
Updated GP_Terms_Of_Service class to singleton pattern
Updated plugin name from "GP Terms of Service Field" to "GP Terms of Service"
Replaced GWTermsofServiceField with GF_Field_Terms_Of_Service class which extends the GF_Field class for better integration with other 3rd party GF plugins