real WIP
code cleanup: create helper method
test: add AckStatusSmsenvoi.get_arcode test
test: add testWriteJson for TrackInfos json serialization
replace Gson with jackson (rationale: jackson now used in smsu-api-admin)
replace json-simple with jackson (rationale: jackson now used in smsu-api-admin)

nb: json-simple requires junit directly. since we remove json-simple and need to require junit explictly
add WS action "MessageStatus" (needed for smsuapi proxy)
smsuapi proxy: replace XFire with simple REST client
drop support for certificate authentication (not compatible with smsuapiadmin < 2.0)
WIP