Rename JSSObject.update() to JSSObject.save() to better reflect role.
Pretty up CHANGELOG.
Implement several small improvements.

- Type checking for JSS instance arguments to JSSObject.
- Rename SearchCriteria property ```list_type``` to match other objects.
- Add **kwargs to all remaining new() methods.
Reimplement class TemplateFromFile as JSSObject.from_file.
Reimplement class TemplateFromString as JSSObject.from_string()