Handling of csv polygon files

[rnyb]

Currently there's a couple of webviz plugins using polygon files (csv format); SeismicMisfit and RftPlotter (others?).
These plugins expects that the header = X_UTME, X_UTMN, Z_TVDSS, POLY_ID
However, we should consider supporting a new header standard = X, Y, Z, ID

For a period of time we could implement support for both versions (with a deprecation warning on the old?).

We could also consider adding a new class for reading polygon files for re-use across plugins

[rnyb]

Plugins to update

• SeismicMisfit (SeismicMisfit - support new polygon header standard #1017)
• RftPlotter (Update RftPlotter so it works with new header for polygon files. #1195)
• SwatinitQC (Update SwatinitQC so it works with new header for polygon files. #1196)