improved get_im_ids

[mellertd]

Description

This addressed issue #2

Added ability to search for im ids by project and plate (in addition to dataset and well, which were there previously).

Added ability to filters lists of image ids based on kv pair and tag.

Also improved some tests and code style.

For reviewers

• Check that the PR title is short, concise, and will make sense 1 year later.
• Check that new functions are imported in corresponding __init__.py.

[erickmartins]

Looks good to me! Squashing and merging.