wam/wash: Implement 'open' functionality, add lots of comments.

This adds wam.FileSystem 'open' functionality to most places.

The wam 'open' message, and the 'stat', 'seek', 'read', and 'write'
sub-messages are plumbed through wam.binding.js classes,
wam.remote.fs.handshake, wam.jsfs.FileSystem, wam.jsfs.RemoteFileSystem,
and wam.jsfs.dom.FileSystem.

This also fills out most js docs for the files it touches.

Finally, 'cp' and 'rm' commands are implemented in wash_executables.js to
make use of the new plumbing.

Change-Id: Iaa11925a296afe849769ff5220f3092c2e3c86f3
Reviewed-on: https://chromium-review.googlesource.com/200638
Reviewed-by: Robert Ginda <rginda@chromium.org>
Tested-by: Robert Ginda <rginda@chromium.org>
libdot 1.9: Add "@eval" directive to bin/concat.sh

* Add an "@eval" directive which evaluates its operand with bash's eval
  builtin, and appends the result to the concat output.

Change-Id: Ic3d76772688e7de87d8806742cc750c8004452f1
Reviewed-on: https://chromium-review.googlesource.com/201693
Reviewed-by: Robert Ginda <rginda@chromium.org>
Tested-by: Robert Ginda <rginda@chromium.org>
wam 1.1: Use changelog version as wam handshake version.

* Pull the latest version from the changelog (during concat), and use it as
  the version number offered/expected in a fs handshake.  Only the major version
  matters for comparison sake.  Changelog versions should jump by a major
  version for each backwards incompatible change.

Change-Id: I6c3f3b5a6ea40dcd0840c7fd9003a05b15cd75cb
Reviewed-on: https://chromium-review.googlesource.com/201694
Reviewed-by: Robert Ginda <rginda@chromium.org>
Tested-by: Robert Ginda <rginda@chromium.org>
nassh 0.8.27.6, saltpig 1.3: Update manifest versions

* Update manifest versions and publish to CWS with updated wam deps.
* Fix saltpig/bin/mkzip.sh to only include nmf/pexe/tar from the
  root directory.

Change-Id: If034100e033891e4dadb0d359690d9549edbe7ad
Reviewed-on: https://chromium-review.googlesource.com/201695
Reviewed-by: Robert Ginda <rginda@chromium.org>
Tested-by: Robert Ginda <rginda@chromium.org>