v3.4.2: Added flip operator (^), fixed MacOs build using brew GCC

Pin matplotlib to latest version 3.6.3 (#169)

v3.3.2: .copy() and sizeof functions.

- Deep copy of PyCtxt using `.copy()`
- `sizeof` functions to get bytesize of all objects
- Adding `compr_mode` to `sizeof` functions to allow check with
compression.

Expose size (B) of save/load serialized objects

Fix Demo_5_CS for Python3.7

update PALISADE submodule to gitlab url (#120)