[ADD] Pdfplumber support

[bosd]

This is a highly opinionated basic implementation of pdfplumber.
I've created this in an attempt to parse invoices with an html style table as mentioned in #359

It's working, but currently I'm developing an integration with camelot.
As Camelot allows more complex table structures to be parsed and a gui to help build the templates.

Creating this PR in case someone needs it.

[bosd]

Propably need to tell the tests to install pdfplumber.
@m3nu Any ideas how to do that?

[bosd]

All ✔️ now!
But in this state it is not something we would like to merge.
Need to clean commits and dependency issue on pdfminer.
Therefore will convert this one back to draft.

[bosd]

depends upon: #395

[rmilecki]

Looks good except for the list of commits in your bosd:pdfplumber branch. There is some merge commit and a lot of work-in-progress commits.

In my personal taste we shouldn't merge such commits into invoice2data' master branch. Those commits don't bring much/any value, make git log a bit messy and make even break git bisect if someone ever tries that.

My personal suggestion / preference would be to squash all those commits into a single one with some clear subject.

[rmilecki]

Nitpicking: I'd replace pdf plumber with pdfplumber for consistency.

[bosd]

In my personal taste we shouldn't merge such commits into invoice2data' master branch.

@rmilecki
I totally agree. Was really struggling on this one. (working on 2 dev systems one windows and one linux machine)
Will try to fiup here. otherwise start over on new branch and pr.