docs: fix typos and common misspellings (#1668)

docs/releases/v2016.1.3.rst

docs/releases/v2016.1.4.rst

docs/releases/v2016.1.5.rst

docs/releases/v2016.1.6.rst

docs/releases/v2016.1.rst

docs/releases/v2016.2.1.rst

docs/releases/v2016.2.2.rst

docs/releases/v2016.2.3.rst

docs/releases/v2016.2.4.rst

docs/releases/v2016.2.5.rst

docs/releases/v2016.2.6.rst

docs/releases/v2016.2.7.rst

docs/releases/v2016.2.rst

docs/releases/v2017.1.1.rst

docs/releases/v2017.1.2.rst

docs/releases/v2017.1.3.rst

docs/releases/v2017.1.4.rst

docs/releases/v2017.1.5.rst

docs/releases/v2017.1.6.rst

docs/releases/v2017.1.7.rst