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/references/http-websocket-apis/public-api-methods/account-methods/noripple_check.md

@@ -15,7 +15,7 @@ The `noripple_check` command provides a quick way to check the status of [the De
 ## Request Format
 An example of the request format:
 
-{% raw-partial file="/_snippets/no-cli-syntax.md" /%}
+{% raw-partial file="/docs/_snippets/no-cli-syntax.md" /%}
 
 {% tabs %}
 
@@ -191,4 +191,4 @@ The response follows the [standard format][], with a successful result containin
 * `actNotFound` - The [Address][] specified in the `account` field of the request does not correspond to an account in the ledger.
 * `lgrNotFound` - The ledger specified by the `ledger_hash` or `ledger_index` does not exist, or it does exist but the server does not have it.
 
-{% raw-partial file="/_snippets/common-links.md" /%}
+{% raw-partial file="/docs/_snippets/common-links.md" /%}