Allow to store Date in UTC

[msaf1980]

go test -race ./...
?   	github.com/lomik/carbon-clickhouse	[no test files]
?   	github.com/lomik/carbon-clickhouse/carbon	[no test files]
?   	github.com/lomik/carbon-clickhouse/cmd/e2e-test	[no test files]
?   	github.com/lomik/carbon-clickhouse/grpc	[no test files]
--- FAIL: TestSlowTimestampToDays (0.00s)
    --- FAIL: TestSlowTimestampToDays/1668106870_2022-11-10T14:01:10-05:00,_UTC_2022-11-10T19:01:10Z_[0] (0.00s)
        date_test.go:59: TimestampDaysFormat() = 19306 (2022-11-10), want 19307 (2022-11-11)
    --- FAIL: TestSlowTimestampToDays/1668193200_2022-11-11T14:00:00-05:00,_UTC_2022-11-11T19:00:00Z_[1] (0.00s)
        date_test.go:59: TimestampDaysFormat() = 19307 (2022-11-11), want 19308 (2022-11-12)
    --- FAIL: TestSlowTimestampToDays/1668124800_2022-11-10T19:00:00-05:00,_UTC_2022-11-11T00:00:00Z_[2] (0.00s)
        date_test.go:59: TimestampDaysFormat() = 19306 (2022-11-10), want 19307 (2022-11-11)
    --- FAIL: TestSlowTimestampToDays/1668142799_2022-11-10T23:59:59-05:00,_UTC_2022-11-11T04:59:59Z_[3] (0.00s)
        date_test.go:59: TimestampDaysFormat() = 19306 (2022-11-10), want 19307 (2022-11-11)
    --- FAIL: TestSlowTimestampToDays/1650776160_2022-04-23T23:56:00-05:00,_UTC_2022-04-24T04:56:00Z_[4] (0.00s)
        date_test.go:59: TimestampDaysFormat() = 19105 (2022-04-23), want 19106 (2022-04-24)
--- FAIL: TestTimestampToDays (0.00s)

As I think, is a cause of go-graphite/graphite-clickhouse#184

This PR also provide a way to switch to UTC in future (need some changes in graphite-clickhouse and/or rebuild points/index/tags tables). See go-graphite/graphite-clickhouse#203

Also, provide fix for #115 (store in UTC)