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/utility-methods/json.md

@@ -46,4 +46,4 @@ An example of a successful response:
 
 The response follows the [standard format][], with whichever fields are appropriate to the type of command made.
 
-{% raw-partial file="/_snippets/common-links.md" /%}
+{% raw-partial file="/docs/_snippets/common-links.md" /%}

docs/references/http-websocket-apis/public-api-methods/utility-methods/ping.md

@@ -86,4 +86,4 @@ The response follows the [standard format][], with a successful result containin
 
 * Any of the [universal error types][].
 
-{% raw-partial file="/_snippets/common-links.md" /%}
+{% raw-partial file="/docs/_snippets/common-links.md" /%}

docs/references/http-websocket-apis/public-api-methods/utility-methods/random.md

@@ -104,4 +104,4 @@ The response follows the [standard format][], with a successful result containin
 * Any of the [universal error types][].
 * `internal` - Some internal error occurred, possibly relating to the random number generator.
 
-{% raw-partial file="/_snippets/common-links.md" /%}
+{% raw-partial file="/docs/_snippets/common-links.md" /%}