docs: move documentation for options from docs/content into backends

In the following commit, the documentation will be autogenerated.

docs/content/b2.md

@@ -265,46 +265,10 @@ start and finish the upload) and another 2 requests for each chunk:
 /b2api/v1/b2_finish_large_file
 ```
 
-### Specific options ###
+#### Versions ####
 
-Here are the command line options specific to this cloud storage
-system.
-
-#### --b2-chunk-size valuee=SIZE ####
-
-When uploading large files chunk the file into this size.  Note that
-these chunks are buffered in memory and there might a maximum of
-`--transfers` chunks in progress at once.  5,000,000 Bytes is the
-minimim size (default 96M).
-
-#### --b2-upload-cutoff=SIZE ####
-
-Cutoff for switching to chunked upload (default 190.735 MiB == 200
-MB). Files above this size will be uploaded in chunks of
-`--b2-chunk-size`.
-
-This value should be set no larger than 4.657GiB (== 5GB) as this is
-the largest file size that can be uploaded.
-
-
-#### --b2-test-mode=FLAG ####
-
-This is for debugging purposes only.
-
-Setting FLAG to one of the strings below will cause b2 to return
-specific errors for debugging purposes.
-
-  * `fail_some_uploads`
-  * `expire_some_account_authorization_tokens`
-  * `force_cap_exceeded`
-
-These will be set in the `X-Bz-Test-Mode` header which is documented
-in the [b2 integrations
-checklist](https://www.backblaze.com/b2/docs/integration_checklist.html).
-
-#### --b2-versions ####
-
-When set rclone will show and act on older versions of files.  For example
+Versions can be viewd with the `--b2-versions` flag. When it is set
+rclone will show and act on older versions of files.  For example
 
 Listing without `--b2-versions`
 
@@ -329,3 +293,7 @@ server to the nearest millisecond appended to them.
 
 Note that when using `--b2-versions` no file write operations are
 permitted, so you can't upload files or delete them.
+
+<!--- autogenerated options start - edit in backend/backend.go options  -->
+<!--- autogenerated options stop  -->
+