fix #287: update image working

[sonalkr132]

closes #287 (hopefully)

Of course we need to add tests. Before that:

• When user click on update he is updating a single image, hence I am not allowing him to select multiple images. However, I am using an array of ActionDispatch::Request so that we can use same function satellite_commit. Am I right?

• When user update an image1.jpg with image2.jpg. We keep both copies of image1 and image2 in tree. Shouldn't we remove image1.jpg from tree?

• Can I take up Validate file uploads #220? We already have Fixed update option #236 but there seems to be no activity on it. Validate file uploads #220 needs to be fixed for me to write tests.

  #Need_Feedback

[sonalkr132]

Fixed in #292