Refactor: Generators and Comprehension

Description/Motivation/Screenshots

This refactoring PR addresses 3 different PEPs:

• PEP 274 - Dict Comprehensions (Python 2.7 + 3.0): This PR uses the dict comprehension syntax where appropriate.
• PEP 289 - Generator Expressions (Python 2.4): This PR replaces list comprehensions with Generator Expressions where appropriate for better memory efficiency.
• PEP 380 - Syntax for Delegating to a Subgenerator (Python 3.3): This PR uses the yield from syntax.

How Has This Been Tested?

Checklist

• My PR was done against the gdb_8_py36_code_refactor branch, not master.
• My code follows the code style of this project.
• My change includes a change to the documentation, if required.
• My change adds tests as appropriate.
• I have read and agree to the CONTRIBUTING document.