Agsconfig

Fixes
-----
- Changed the default bool-to-string serialization to use lowercase, as this seems to be a common requirement

Fixes
-----
- Fixed a bug where extensions weren't being enabled

New Features
---------------
- Added support for NAServer extension on MapServer
- Added support for editing JSON for extensions

New Features
---------------
- Added support for GeodataServer
- Improved error reporting

Fixes
-----
- Fixed `allowed_compressions` property for ImageServer services when editing the JSON configuration

New Features
---------------
- Added `save_a_copy`/`export` functionality to the editors

Fixes
------
- Fixed issue with Python2/3 compatibility that could break functionality

New Features
- Add support for setting the default JPEG compression quality on ImageServer services

Fixes
- Makes potentially missing property of the ImageServer service type creatable in SD Drafts