Preconditions dev

[DowntonCrabby]

• Created the pre_post_condtions.py file with pre and post condition functions that assert various very straightforward and simple things like meeting thresholds, id types etc,
• refactored retrieval of well known file filepaths to be more modular and work with a dictionary so it is easier to see what well known file ids and file names are relevant
• added several other dictionary systems to act as constants and make code more readable and understandable.

[DowntonCrabby]

For the well known files, using the database may be better practice. Is a hard-coded dictionary required?

• the lims database contains well known files for tons of different projects. I thought a dictionary that contains just the well known files related to visual behavior would make it more explicit and readable as to what my code is doing. I also had to individually look up what types of attachable id's to use. there might be another way to programmatically get that information about the attachable id type from the lims database but I'm not sure what it is.

_Is there a reason you built your own lims connection and used mixin.select() rather than using database.py's db.limsquery?

• the db.lims_query was developed at the same time as this/in parallel. Unfortunately we now have some redundancy.

[DowntonCrabby]

@seanmcculloch I know there were some changes you wanted to make. Is that still the case?

[seanmcculloch]

Using the lims / mtrain credentials works, though there is redundancy with database.py. Removing this redundancy is outside of the scope of this PR, so no changes needed.