Default format for storing files should be ProbModelXML

[Francisco Javier Díez]

In OpenMarkov 0.3 the default format for encoding networks is "Elvira file (.elv)". It should be "ProbModelXML 0.5 (.pgmx)", as in previous versions.

[Manuel Arias]

The default format should be 0.6, because the 0.5 is only internal and will no longer exists.

[Manuel Luque]

Currently, the default format in OpenMarkov 0.3.0 when saving a file is "ProbModel 0.2 (*.pgmx)". Please, Manuel, consider if the type of this issue should be modified from "enhancement" to "bug".

[Manuel Arias]

Default format is OpenMarkov 0.5