Log exception when step assembly can't be loaded and continue

[icnocop]

Fixes https://github.com/SpecFlowOSS/SpecFlow.VS/issues/109

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue).
• [ ] New feature (non-breaking change which adds functionality).
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected).
• [ ] Performance improvement
• [ ] Refactoring (so no functional change)
• [ ] Other (docs, build config, etc)

Checklist:

• [ ] I've added tests for my code. (most of the time mandatory)
• [x] I have added an entry to the changelog. (mandatory)
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.

[SabotageAndi]

@gasparnagy Would this really fix it? Of course only after an update of the NuGet package in the VS extension.