HADOOP-11394. hadoop-aws documentation missing. Contributed by Chris Nauroth.

(cherry picked from commit 9458cd5bce20358e31c0cfb594bc545c7824b10d)
HADOOP-11396. Provide navigation in the site documentation linking to the Hadoop Compatible File Systems. Contributed by Chris Nauroth.

(cherry picked from commit cbfb996fb4787e9d4bbaee1d01e3eca2caf0ce55)