Add time partitioning field to google_bigquery_table resource (hashicorp#1240)

* Add time partitioning field to google_bigquery_table resource

* Fix flatten time partitioning field to google_bigquery_table resource

* Add resource bigquery table time partitioning field test

* Move resource bigquery table time partitioning field test to basic

* Add step to check that all the fields match

* Mark resource bigquery table time partitioning field as ForceNew

* Add time partitioning field test to testAccBigQueryTable config

Author: amatellanes

docs/r/bigquery_table.html.markdown

@@ -81,6 +81,10 @@ The `time_partitioning` block supports:
 * `expiration_ms` -  (Optional) Number of milliseconds for which to keep the
     storage for a partition.
 
+* `field` - (Optional) The field used to determine how to create a time-based
+    partition. If time-based partitioning is enabled without this value, the
+    table is partitioned based on the load time.
+
 * `type` - (Required) The only type supported is DAY, which will generate
     one partition per day based on data loading time.