Project File: Use rsp location as starting point for import of relative file path

[hhgs]

Error when resinsight is started in an arbitrary folder, importing a project with relative file path references:

resinsightdev $ QIODevice::read (QFile, "resinsight/input/geogrid_gfssl.grdecl"): device not open terminate called without an active exception

Note! Other applications do also use current working directory as starting point for relative paths. So using location of project file as reference could be a fall back when files are not found using CWD.

[hhgs]

Crash when starting ResInsight at "wrong" working directory compared to relative paths in the project file: QIODevice::read (QFile, "resinsight/input/geogrid_gfssl.grdecl"): device not open terminate called without an active exception

If missing Project include files, give message about which file is missing, and proceed with opening Project file.