Create new table definitions

[micah-prime]

Let's create all the new table definitions as outlined in the re-organization diagram

Tables to create are

• instruments @micah-prime
• observers @micah-prime
• Restructure - DOI table #133
• Restructure - measurement type table #134
• sites
• campaigns @jtmaze

Each table can have it's own file (like @jomey 's reorg)

Tables to update are:

• Restructure - ImageData #132
• Restructure - Point Data #136

[micah-prime]

These are being pushed to the dev branch, so PRs can be made there

[jomey]

Noting that we should also add some indexes on the foreign key columns.
One example on how to do this:

name = Column(String, index=True)

[jomey]

Other definition to consider is to require the presence of an attribute/column via NOT NULL

name = Column(String, nullable=False)

https://docs.sqlalchemy.org/en/20/core/metadata.html#sqlalchemy.schema.Column.params.nullable

[jomey]

Saving a reference on why we don't need to set limits on varchar
https://wiki.postgresql.org/wiki/Don%27t_Do_This#Don.27t_use_varchar.28n.29_by_default