Gather all global constants, and make their naming consistent

Created by: pastly

In sbws/globals.py we have

• G_PKG_DIR where the G was supposed to stand for global
• and other ALL_CAPS constants

In sbws/__init__.py we have

• version
• res_proto_ver
• wire_proto_ver

---

• pick one file or the other.
• Pick a naming scheme. G_FOO or FOO is what I'd prefer.
• If we change the name or location of version, we need to update setup.py and docs/source/conf.py and (if we've merged @juga0's V3BwHeader PR) sbws/lib/v3bwfile.py