Handle memories

[mlyoung101]

We need to do something about memories. Currently, the test memory.ys fails with this:

Replicating 4 collected items for logic cone 1
    Replicating ElementWireNode $0\data_o[31:0][0]
    Replicating ElementCellNode mem
ERROR: Assert `!packed_memids.count(memid)' failed in kernel/rtlil.cc:2246.

Quick and dirty: Ignore memories and issue a warning.

Competent: Triplicate memories. This could be extremely complicated.

[mlyoung101]

I believe this may be fixed and is instead crashing due to #22

[mlyoung101]

This seems to be an issue with how we handle (* tamara_ignore *) - we still want to include ignored nodes in the backwards BFS search, but not use them for TMR or anything. Otherwise, if we terminate the search too early, we don't consider nodes that are past say the memory cell.