feat(mbuild): media-upload doit() methods

It's just a first step, and even though the generation works well,
I am still missing the right Rust code. Will have to simplify ...

etc/api/shared.yaml

@@ -18,6 +18,8 @@ api:
   terms:
     # how to actually do something with the API
     action: doit
+    # when a resource is supposed to be uploaded
+    upload_action: upload
   templates:
   # all output directories are relative to the one set for the respective API
     - source: README.md

gen/youtube3/src/cmn.rs

@@ -1,6 +1,8 @@
 // COPY OF 'src/rust/cmn.rs'
 // DO NOT EDIT
 use std::marker::MarkerTrait;
+use std::io::{Read, Seek};
+use std::borrow::BorrowMut;
 
 /// Identifies the Hub. There is only one per library, this trait is supposed
 /// to make intended use more explicit.
@@ -30,3 +32,7 @@ pub trait Part: MarkerTrait {}
 /// Identifies types which are only used by other types internally.
 /// They have no special meaning, this trait just marks them for completeness.
 pub trait NestedType: MarkerTrait {}
+
+/// A utility to specify reader types which provide seeking capabilities too
+pub trait ReadSeek: Seek + Read {}
+impl<T: Seek + Read> ReadSeek for T {}