[ADQL] BOX+CIRCLE+POLYGON : make coord. sys. optional and allow POINT values

src/adql/parser/ADQLQueryFactory.java

src/adql/parser/grammar/adqlGrammar201.jj

src/adql/query/operand/function/geometry/BoxFunction.java

src/adql/query/operand/function/geometry/CircleFunction.java

...dql/query/operand/function/geometry/DistanceFunction.java

...dql/query/operand/function/geometry/GeometryFunction.java

src/adql/query/operand/function/geometry/PointFunction.java

...adql/query/operand/function/geometry/PolygonFunction.java

src/adql/translator/PgSphereTranslator.java

test/adql/parser/TestADQLParser.java