implement packet API to read information about AR status

A new mailbox service shall be defined and implemented. The service shall offer possibility for Hilscher to detect issues in AR establishment or shutdown related to application behavior.

The service shall return the uptime ms value.

The service shall return per AR 

• state of AR (CMDEV)
• is AR_Check_Ind pending? if yes, since which uptime ms value?
• is Check_Ind pending? if yes, since which uptime ms value?
• is AR_State_ind pending? if yes, since which uptime ms value? (if yes, which state exactly is pending?)
• is Event_Ind pending? if yes, since which uptime ms value? (if yes, which Event is requested)
• is WriteRecord pending? if yes, since which uptime ms value?
• was ApplicationReady requested by application?