add verbose argument to load_pretrained_model

[acocac]

It would be great to add a verbose parameter to control printing of dependencies installation messages.

[quantumjot]

Could add the -q flag to the pip install?

https://github.com/alan-turing-institute/scivision/blob/bd7d2793f043391cef2fcd382f88245d9472bf36/scivision/io/installer.py#L30