BigQuery: moves Row class out of helpers and updates docstrings (#4291)
BigQuery: moves Row class out of helpers and updates docstrings (#4291)

* moves Row class out of helpers and updates docstrings to specify Row as rtype

* updates docstring references to classes to include the appropriate module

* breaks up imports to different lines

* renames single letter variables and fixes string formatting

* adds todo to fix circular import

* updates references to bigtable's Row class to differentiate from bigquery's Row class

* Revert "adds todo to fix circular import"

This reverts commit 1c2bbb01a5fa70d5ddbaf81576e84e760d8b9f6e.

googleapis/python-bigtable,googleapis/python-bigtable