documentation overhaul (#353)

* ident
* remove $Id$ tags from rcs software which has been retired
* make an effort to sync required mib docs with actual code
* sync even more docs with what code actually does
* some whitespace nits
* fixup example to use snmpv2 for all but the most ancient devices
* remove blurb to find more specific snmp::info classes for classes
  which alrdy are as specific as they can get (eg snmp::info::layer3::vmware
  doesn't need info on to find a specific module since there ain't none)
* rename all sub {vendor} strings to lowercase vendor, if cisco, juniper
  and arista can be lowercase, so can be all the rest.
* fix tests
* spread some use warnings around
* use $ instead of @
* remove defines that are included via parent classes
* use strict + warnings
* remove alrdy included modules
* add comma after last list item
* typos
* mibs are found in our mib repo, not on the cisco site
* documentation fixes

lib/SNMP/Info/Layer3/Passport.pm

@@ -713,7 +713,7 @@ sub e_index {
     my $model = $passport->model();
     my $rc_ps_t = $passport->rc_ps_type() || {};
 
-    # We're going to hack an index: Slot/Mda/Postion
+    # We're going to hack an index: Slot/Mda/Position
     # We're going to put chassis and power supplies in a slot
     # which doesn't exist
     my %rc_e_index;