External, side modules

Some external, side modules: modules needed for some optional purposes of epygram, often developped along, but that may be used from outside.

• arpifs4py — Interface functions to some Arpege/IFS functions
• pyexttiff — Classes to read Tiff
• usevortex — Proxies to reach resources using Vortex
• griberies — utilities around GRIB
• vgrid — Contains handling of Hybrid-Pressure vertical grid generation and plotting.