Revisit H3C Exec-Privilege

Try to match H3C terminology as close as to their documentation.

- The Attribute name seems to not exactly match documentation,
  found consistently user i.e. in:
  - H3C S12500: Configurations Guides
  - H3C WA Series: Security Configuration Guide

- Rename privilege levels to match H3C's documentation
  (previously likely more 3Com-ish). The levels naming
  are being used consistently mentioned throughout:
  - H3C SecPath F1000-E: Operational Manual
  - H3C S5500-SI: Operation Manual
Extend the H3C dictionary based on public manuals

Try to extend the H3C dictionary based on what is scattered on
their pages. At least most of it is found quite consistently in
the product-specific "Security Configuration Guides".

This compilation/crosschecking is based H3C documentation for
listed devices:
- H3C S12500 and S6800 Switches
- H3C WA WLAN Access Points
- H3C MSR Routers

Remarks:
Does not stick with H3C's use of of underline in attribute naming.