Gravity Forms Signature Addon 4.6.0

- Added security fixes.
- Added query parameter to return signature as transparent image.
- Added GPL to plugin header.
- Updated Plugin URI and Author URI to use https.

- Added security enhancements.

- Added compatibility with Gravity Forms 2.3.
- Updated IeModalFix init option to only be set for IE browsers; fixes issue with FireFox with 3+ paths on a signature.
- Fixed a JavaScript error which could occur in the form editor with Gravity Forms 2.3-beta.
- Fixed an issue where the field could be populated with the value from another form on the same page if both fields have the same ID.
- Fixed an issue where the signature file could remain after the entry was permanently deleted.