Closes #436 (and #122?): Add options to disable smooth cables and physics

[dremerb]

Although both issues has status "under review", this maybe makes the decision to accept the issue easier.

PR adds settings to make cable renderings straight lines, as proposed in #436.
Line style is controlled by an option in the "Individual Options".
I am currently working with ~200 hosts and 500+ cables, this change makes the graph a lot clearer in my opinion.

Two side effects:

• With physics enabled, there is a more movement in the graph - but I want to propose another PR that allows turning that off anyway, maybe that synergy works out fine
• Since cables are straight lines now, they are "bundled" (Combine redundant connections #122). Or rather plotted on top of each other. The cable's shadows overlay each other as well, which may be considered "not pretty", but accidentally works well as an indicator of multiple connections between two ends.

Fixing the shadows could be done extracting edges.append(create_edge(...)) calls into a dedicated function and ignoring duplicate connections.

[mattieserver]

Can you maybe change the name of the vars you added?
Maybe make it 'straight_cables' or something like that.

[mattieserver]

Looks good, will merge after testing

[dreng]

You have overlooked the saved filters.

api/views.py, line 112 and below
views.py, line 713 and below.

[dreng]

You have not taken get_query_settings() into account in utils.py.

[dreng]

We need to finish compatibility with NetBox 4.0 first. This PR may need to be rebased after that.

[mattieserver]

I will try to test/merge this this weekend.