Database normalization features

[daniel-skovenborg]

Sorry, I know this is a very large pull request and that your guidelines encourage to ask before implementing new features. However, I urgently needed this feature enough to implement it, even if it will only ever live in my own fork. I am (for) now done with the task for which the code was designed and think it's ready to be adapted, if you want it.

Description

The Danish National Archives requires the database to be 1NF (exported as SIARD-DK). The following features allows exporting a database for this purpose without creating an auxiliary database.

• Allow exporting custom views indistinguishable from tables, specifying PK's and FK's
• Helper configuration module for normalizing array and JSON columns to tables (custom views)
• Support database preparation statements (for creating temporary tables used in custom views)

The normalization configuration module currently has only the string pattern options implemented that I needed where my own requirements differed from what I deemed to be the proper default.

[daniel-skovenborg]

The code has only been tested on PostgreSQL. I believe I have written the array normalization SQL without non-standard features, though.