Bug-731: PCEPErrors enum with error-type and error-value

-enum backed with inverse mapping - look-up enum for type and value
-deleted PCEPErrorMapping class - got rid of Sonar "Magic Number" warnings
-AbstractMessageParser - merge two createErrorMsg methods to one

Change-Id: I94a688427ae606eecdbafffa09d29e364f183526
Signed-off-by: Milos Fabian <milfabia@cisco.com>