Add possibility to not upscale for "Scale and crop" effect

Problem/Motivation

The "Scale" effect provides a choice for whether to upscale. But "Scale and crop" provides no such choice and forces upscale.

Proposed resolution

Allow to choose whether upscaling should be performed or no in "Scale and crop" effect.

User interface changes

Added "Allow Upscaling" checkbox on "Scale and crop" effect edit form.