Environment class does not support weather files with negative longitudes

[giovaniceotto]

The current implementation of the Environment class raises an error whenever weather files which make use of negative values for longitude are imported. This error happens in the processNetCDFFile method.

Both longitude ranges, from 0 to 360 and from -180 to 180 should be supported.

One alternative is to try using the 0-360 range and except the -180 to 180 range if an error is raised. This order is motivated by the fact that global models generally use 0-360 ranges, where regional models from the left hemisphere generally use -180 to 180.

[giovaniceotto]

Simple fix applied in the last commit.

The solution was to verify if a file used the range from -180 to 180 by detecting negative values in its longitude list. If so, an appropriate conversion is made to the input longitude to fall into this range (if bigger than 180). If not, the previous method is used, which was made for files ranging from 0 to 360.