Support for Salome Platform 9.8

[trelau]

Version 9.8 is available which looks like it includes proper support for Netgen 6.2.

Note that Salome still uses a patched version of OCCT 7.5, so unclear how feasible upgrading OCCT version will be...

[trelau]

Since upstream Salome is still using a patched version of OCCT 7.5.3, general approach will likely be:

• Upgrading current SMESH to OCCT 7.5.3 (it is using 7.5.2). Cut a release with OCCT 7.5.3 support but no other changes.
• Upgrading to SMESH 9.8 using OCCT 7.5.3 (before messing with challenges around migrating to OCCT 7.6). This would include support for Netgen 6.2.
• Then consider #54

I think there was a good number of API changes in OCCT 7.6 (e.g., module renaming or removing), so start by getting SMESH updated to upstream Salome with consistent OCCT versions. If there is a lot of patching to do to support OCCT 7.6, it might also be worth seeing how long it might be before Salome updates to OCCT 7.6. Although, this means that the pace of these projects is set by Salome (and not OCCT updates).