Add loading indicator while waiting for files responses

[olizilla]

If the user copies the root a data-set into their MFS, it is not automatically recursively fetched. (it probably should be)

If a user drills down into a data-set that hasn't yet been fetched, the UI freezes with no information as to what is going on.

A quick test

$ ipfs dns arewedistributedyet.com
/ipfs/QmeANzfbKFunvrenGDVbAttucJvNF6wrWH96QeSWdmgGy6

$ ipfs files cp /ipfs/QmeANzfbKFunvrenGDVbAttucJvNF6wrWH96QeSWdmgGy6 /awdy

Now navigate to the files page in the web ui and click on the /awdy entry. It taks a few seconds to load, while the data is fetched. There is no indication to the user. A larger data set can hang things for minutes.

[alx696]

@olizilla Better to add progress indicator for add file and download file. Now, It looks like already have one, but not work. The progress info only show when 100%, no tips for a long time. Especially when the file is large.