BFS Push/Pull, SSSP, SpMSpV

[kirillgarbar]

Proposed Changes

• General and bool SpMSpV
• Sparse BFS
• Push/Pull BFS
• Dense SSSP
• Some useful methods
• Memory leaks fixed in Radix
• Segmented reduction on options
• Sparse-Dense map2 for vectors
• Stubs for empty vectors

Types of changes

What types of changes does your code introduce to GraphBLAS-sharp?
Put an x in the boxes that apply

• [x ] Bugfix (non-breaking change which fixes an issue)
• [x ] New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• [x ] Build and tests pass locally
• [x ] I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added necessary documentation (if appropriate)