By default, files with the prefix "/bin/", "/usr/bin/" and "/usr/local/bin/"
will have a new export flag "x" in the 4th byte of the flag section of the
bundle Manifest.
The user can override this by using a new keyword "un-export()" in
the bundle definition file.
E.g. un-export(/usr/bin/file2)
Note: The export flag is at a bundle-file level and hence does not get
written to the Full manifest.
Fixes#708
Includes bat tests for the export flag feature.
Also, adds an entry for the content-chroot tests to Travis.
Signed-off-by: Reagan Lopez <reagan.lopez@intel.com>