Update of links in the docstrings (sammchardy#1590)

* spot links in the docstrings updated

* Margin api docstrings updated

* Docstrings for fapi endpoints updated

* Missing dapi endpoints added and dapi docstrings updated

* Missing eapi endpoints added and docstrings updated

* papi endpoints updated

* futures_coin_v1_put_order returned

* Wallet links updated

Author: yzh-pelle