#2 Improve OPJ files import

[Anonymous]

* Use native byteorder (=) instead of little-endian (<) for unpack expressions.
Should handle little-endian/big-endian files transparently (not tested).

* Added creation of Project Folders and Matrix windows.
Added description of Graphs as Note windows.

NOTE: Import of Matrices is slow mainly because elements have to be
converted one by one. SciDAVis Matrix Python API should have a
replaceValues() method to convert the whole Matrix at once.

To convert multiple files at once, a Python API to delete a SciDAVis
project tree is needed.

[Anonymous]

Add project tree and matrix windows

[Knut Franke]

Duplicate of #2990795 (patches are identical).