Updata Controller javadoc to inform that stream content may be fully loa...

...ded in memory

Added the following comment on all renderBinary methods that accept an InputStream but no length parameter:
"Content is fully loaded in memory, so it should not be used with large data."

See the RenderBinary class: all data is copied into a ByteArrayInputStream (response.out). This can lead to OutOfMemoryErrors, so I think should be documented.