Default Volume Size is too small (500 MB)

Move this to a variable at the top of the deploy.sh script and set it to a more reasonable default (5 GB?). This will allow the user to easily configure a size.

Two variables will be needed to allow configuring the Postgres storage size separately from the rhamt web size (typically RHAMT web needs much more storage than the DB).

NOTES:

• Merge to master and 4.0.x branch
• Send note to Andrea when done to get the docs updated.