EPyGrAM

Commit commit:e0dcee6

netCDF
Several improvements w.r.t. convention CF-1.6 and geometry.
(Almost full-) Compatibility with the forthcoming SURFEX v8.1 netCDF outputs.

EPYWEB
Integration of EPYWEB: a Vortex+Epygram HTML interface for plotting fields from MF operational suites and OLIVE experiments.

Other new features
Pre-staging mode in usevortex
Function fields.psikhi2uv()
Function util.datetimerange()
Computation of wind direction

Miscellaneous
Porting fixes for Mageia6
More flexible colormaps scalings (as radar)

And a quantity of fixes !...