added save options to Imagine plugin presets

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

I needed to change the save quality settings of thumbnails. With this you can set the save options in the preset.

See: http://imagine.readthedocs.org/en/latest/usage/introduction.html#save-images