Added tests that assert that we can store metadata within the diffs

We want to be able to store diffs within the archives and these tests
assert that this functionality will be correct when built.
Added ability to add metadata to the diffs

Now this program can include a .info file with whatever content we
might need to describe the file. This way, renaming the file will not
lose the information about the content (if the user chooses to excercise
this feature).
Bumped code version to 0.4

New metadata inclusion functionality is now part of this so the version
has been increased.
Merge pull request #15 from endlessm/eos-shell/3985

AppUpdater: Add ability to include metadata files in diffs