PROTON-2201, PROTON-2154: drop version back to 0.31.0-SNAPSHOT
PROTON-2201, PROTON-2154: drop version back to 0.31.0-SNAPSHOT

This reverts commits c2384ecdc7b7490fa2ed95fc121d8188122661e3 and b6532632d6b0877136621daeba55b2e105d810d2.

apache/qpid-proton,apache/qpid-proton,gemmellr/qpid-proton,ssorj/qpid-proton,ssorj/qpid-proton,apache/qpid-proton,astitcher/qpid-proton,ChugR/qpid-proton,astitcher/qpid-proton,apache/qpid-proton,apache/qpid-proton,astitcher/qpid-proton,ssorj/qpid-proton,gemmellr/qpid-proton,astitcher/qpid-proton,ChugR/qpid-proton,astitcher/qpid-proton,ChugR/qpid-proton,apache/qpid-proton,ChugR/qpid-proton,astitcher/qpid-proton,gemmellr/qpid-proton,ChugR/qpid-proton,ssorj/qpid-proton,ssorj/qpid-proton,ChugR/qpid-proton,ssorj/qpid-proton,gemmellr/qpid-proton,gemmellr/qpid-proton,gemmellr/qpid-proton