Fix reloading skills system
Fix reloading skills system

==== Fixed Issues ====
One exemple is reloading pairing skill after skill update (30-60 seconds)
results in a new pairing code being generated.

====  Tech Notes ====
Now compare individual skill modification dates and not a global last
modified skill.

forslund/mycroft-core,MycroftAI/mycroft-core,MycroftAI/mycroft-core,aatchison/mycroft-core,linuxipho/mycroft-core,Dark5ide/mycroft-core,aatchison/mycroft-core,forslund/mycroft-core,linuxipho/mycroft-core,Dark5ide/mycroft-core