fixes for [TC-1557], changes in HTTPClient.js, now it composes Blob correctly

Ti.Blob does not do Base64 enc/decoding as specified in the docs

The bug affects  assigning images to ImageView mainly. According to documentation it has property image(images). On MobileWeb it marked as unsupported, but really the issue is Blob that contains binary data(ImageView and documentation expects it to contains base64). Main factory for our Blobs is HTTPClient (e.g. load image async and set it into image view) and all fixed are inside it.
Additional small fix is setting properties Blob.file and Blob.nativePath to real values(old version ignore it).