Add support for multi tasking / multiple projects

[Kenneth Stwolinsky]

It is common to work on several projects at the same time. Many times I am creating a complex project that will take a long time to model shadows or define the system, when I have to review another project or create a more urgent project; Currently I have to save my complex project, close it, open the new project, finish it, open the old one and be able to continue working.
It would be better to have the option to multitask, even if it's just two windows.

[dtarin]

You can open multiple instances of pvsyst. It will tell you another instance is open, just click to get past and you can work on any number of projects at same time.