Update Italian translations.

Thanks to roberto Alacevich for the translations.

src/main/resources/assets/org/orekit/rugged/RuggedMessages_it.utf8

-# internal error, please notify development team by creating an issue at {0}
-INTERNAL_ERROR = <MISSING TRANSLATION>
+# internal error, contact maintenance at {0}
+INTERNAL_ERROR = errore interno, contattare l''assistenza a {0}
 
 # no data at indices [{0}, {1}], tile only covers from [0, 0] to [{2}, {3}] (inclusive)
 OUT_OF_TILE_INDICES = nessun dato agli indici [{0}, {1}], il quadrante non copre che da [0, 0] a [{2}, {3}] inclusi
@@ -59,10 +59,10 @@ DEBUG_DUMP_NOT_ACTIVE = dump di debug non attivo per questo thread
 CANNOT_PARSE_LINE = impossibile analizzare la linea {0}, file{1}: {2}
 
 # light time correction redefined, line {0}, file {1}: {2}
-LIGHT_TIME_CORRECTION_REDEFINED = <MISSING TRANSLATION>
+LIGHT_TIME_CORRECTION_REDEFINED = Correzione luce-tempo ridefinita, linea {0} del file {1}: {2}
 
 # aberration of light correction redefined, line {0}, file {1}: {2}
-ABERRATION_OF_LIGHT_CORRECTION_REDEFINED = <MISSING TRANSLATION>
+ABERRATION_OF_LIGHT_CORRECTION_REDEFINED = Correzione dell''aberrazione stellare ridefinita, linea {0} del file {1}: {2}
 
 # tile {0} already defined, line {1}, file {2}: {3}
 TILE_ALREADY_DEFINED = quadrante {0} già definito, linea {1}, file {2}: {3}
@@ -89,7 +89,7 @@ UNSUPPORTED_REFINING_CONTEXT = il refining che usa {0} istanze rugged non è ges
 NO_LAYER_DATA = nessun dato atmosferico all''altitudine {0} (altitudine più bassa: {1})
 
 # step {0} is not valid : {1}
-INVALID_STEP = <MISSING TRANSLATION>
+INVALID_STEP = Step {0} non valido: {1}
 
 # range between min line {0} and max line {1} too small {2}
-INVALID_RANGE_FOR_LINES = <MISSING TRANSLATION>
+ INVALID_RANGE_FOR_LINES = Scarto fra la linea min {0} e la linea max {1} troppo piccolo {2}