Rename Point to Points

[lilli-nishikawa]

Proposal:
According to Point definition, Point has only one field. However, influxdb-client-python allows Point class to has fields, like so:

influxdb-client-python/tests/test_point.py

Lines 71 to 94 in 854fc6c

	def test_FieldTypes(self):
	point = Point.measurement("h2o") \
	.tag("location", "europe") \
	.field("long", 1) \
	.field("double", 250.69) \
	.field("float", 35.0) \
	.field("integer", 7) \
	.field("short", 8) \
	.field("byte", 9) \
	.field("ulong", 10) \
	.field("uint", 11) \
	.field("sbyte", 12) \
	.field("ushort", 13) \
	.field("point", 13.3) \
	.field("decimal", 25.6) \
	.field("decimal-object", Decimal('0.142857')) \
	.field("boolean", False) \
	.field("string", "string value")
	expected = "h2o,location=europe boolean=false,byte=9i,decimal=25.6,decimal-object=0.142857,double=250.69," \
	"float=35,integer=7i,long=1i,point=13.3,sbyte=12i,short=8i,string=\"string value\"," \
	"uint=11i,ulong=10i,ushort=13i"
	self.assertEqual(expected, point.to_line_protocol())

So, I think that we should rename Point class to Points class.