add preliminary support for exinda / gfi traffic shapers (#283)

* exinda support

* exinda support

* add exinda hint

needed to identify exinda devices.

* mentin exinda in overview and link docs

* overwrite layers to l2/3/4/7

* get uptime from exinda mib

now matches uptime reported by cli & web interface.

* single quotes preferred

* to much copy/paste

* merge 3.63

* some more functions added. also general cleanup

* Update .travis.yml

* a few fixes

* Update .travis.yml

* Update .travis.yml

* revert

* revert

META.yml

@@ -160,6 +160,9 @@ provides:
   SNMP::Info::Layer2::CiscoSB:
     file: lib/SNMP/Info/Layer2/CiscoSB.pm
     version: '3.63'
+  SNMP::Info::Layer2::Exinda:
+    file: lib/SNMP/Info/Layer2/Exinda.pm
+    version: '3.63'
   SNMP::Info::Layer2::HP:
     file: lib/SNMP/Info/Layer2/HP.pm
     version: '3.63'