Understand, document and clean up memory

## Type of Issue

Select the type of issue:
- [ ] Bug report (to report a bug)
- [ ] Feature request (to request an additional feature)
- [x] Tracker (I am just using this as a tracker)
- [ ] Refactor request
- [ ] Documentation Ask

## Checklist

Use this checklist if you are using this issue as a tracker:

- [ ] How to use basic_search, more examples of keywords
- [ ] Clean up in for example mc_memory_nodes -> explain attributes of tables in a doc perhaps. Things like : NODE_TYPE,
- [ ] Consistent naming for things like : ref_type
- [ ] Mention in the doc that BlockObjects and InstSegNodes are under the same table ReferenceObjects
- [ ] Should we get rid of BlockObjects for MC?
- [ ] Right now we have basic_search as well as get_filters and get_filters_from_lf used throughout - we should stick with one consistent way of querying memory for a filters subdict for our use cases.
- [ ] Document what possible ways and APIs there are to read / write / query memory
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- [ ] Task 2
- [ ] Task 3 ...