adding module path in imap_processing - fixes

[tech3371]

Change Summary

Adding imap_processing module path in the imap_processing init.py file and using it in decom code.

Overview

This issue came up when I was trying to install imap_processing in a dockerfile using pip and then calling decom code. Previously, I have hard coded the path and it become irrelevant when it was installed using pip.

Updated Files

• imap_processing/init.py
  • Add way to get current path where imap-procesing pip module is located
• imap_processing/swe/decom_swe.py
  • use above path to point to swe's decom packet definition

[greglucas]

We should think about what we want/need available in the root namespace later, and whether we should add a configuration dictionary with data paths, or add an __init__.py file to the packet_definitions directory so that path is directly discoverable in the installed package.

This can all be easily updated later, so this is a good approach to start with so we don't overcomplicate things right away.