fixed netlist generation and file structure for pcells

[adityakak27]

• changes made in PR 76 have been fixed, naming of netlist obj has been reverted to match original naming and avoid breaking other stuff
• duplicates from ATLAS folder have been removed, only the pcells in blocks/elementary/<pcell_name> exist now, and function as intended. same for evaluator box.
• TODO: opamp placement to still be decided, kept in ATLAS/ for now

[AL-255]

Same comment as before:

This is a good cleanup of the existing code.
What still needs to be done: remove current_mirror.py, diff_pair.py, fvf.py, lvcm.py, opamp.py‎, transmission_gate.py. They're duplicates of what's in the upper level, created as a temporary hack.

Please commit the same changes to those files and remove them from the ATLAS folder completely.

After this, we can look at Erin's PR #70 ‎