Re-levelization: move non-docs content, rename content→docs

For better URLs, the content folder has been renamed 'docs' and all
other files have been moved up a level. Also, non-docs images have been
moved to the static folder at the top level where they belong.

Many relative paths had to be fixed to make this work.

docs/tutorials/quickstart/send-payments-using-python.md

@@ -18,7 +18,7 @@ The XRP Ledger (XRPL) is a robust, secure, customizable service. You can create
 
 This quickstart describes a test harness interface you can build to try out the XRP Ledger. The test harness displays multiple accounts, so that you can transfer tokens from one account to the other and see the results in real time. The image below shows the Token Test Harness at the completion of step 4.
 
-[![Quickstart Tutorial Window](/img/quickstart-py15.png)](/img/quickstart-py15.png)
+[![Quickstart Tutorial Window](/docs/img/quickstart-py15.png)](/docs/img/quickstart-py15.png)
 
 That is a lot of fields and buttons, all working together to perform some significant practical tasks. But getting _started_ with the XRP Ledger is not that complicated. When you eat the elephant a bite at a time, none of the tasks are difficult to consume.
 
@@ -53,6 +53,6 @@ To get started, create a new folder on your local disk and install the Python li
 pip3 install xrpl-py
 ```
 
-Download the python [Quickstart Samples](https://github.com/XRPLF/xrpl-dev-portal/tree/master/content/_code-samples/quickstart/py/)<!-- {.github-code-download} -->.
+Download the python [Quickstart Samples](https://github.com/XRPLF/xrpl-dev-portal/tree/master/_code-samples/quickstart/py/)<!-- {.github-code-download} -->.
 
 **Note:** Without the Quickstart Samples, you will not be able to try the examples that follow.