add SACPZ write support for Inventory (tested against one station served by IRIS SACPZ WS)
changelog
clarification for DIP header comment in SACPZ output
Response.get_paz() returns deepcopy now, much safer

additional minor fixes
Merge pull request #879 from megies/write_sacpz

add SACPZ write support for Inventory
Fix build errors.

One missed print statement and one minor flake8 warning.