Updated Launch chapter

As part of the installation guide improvement project, I performed
the following operations on the Launch chapter:

1) Split monolithic file with instructions for nova networking into
   separate files for nova and neutron networking.
2) Updated instructions in each section to account for differences
   between nova and neutron networking.
3) Updated other sections and glossary as necessary.

Change-Id: I7faaadc0787cf85d816c7c2aab1247ecc77195b2
Partial-Bug: #1291071
Implements: blueprint networking-install-guide-improvements
Merge "Updated Launch chapter"