It is now possible to upload qcow2 images directly. These images will be
converted to raw disk images directly on the cloud server.
In the CLI you can use the new `--format=qcow2` flag to upload qcow2
images. In the library you can set `UploadOptions.ImageFormat` to `FormatQCOW2`.
Because of the underlying process, qcow2 images need to be written to a
file first. This limits their size to 960 MB at the moment. The CLI
automatically checks the file size (if possible) and shows a warning if
this limit would be triggered. The library accepts an input with the
file size and logs a warning if the limit would be triggered.
Generate the help pages using `cobras` builtin functionality and commit
them to the repository. This gives users to ability to review the
options of `hcloud-upload-image` without having to install it first.
