[#1550] Show the file name when uploading a resource

Hiding it is bad makes it hard for the user to check its URL (although it makes
it more difficult for her to change it by mistake).

When you first upload, some browsers have a safety feature to not disclosing
the file's full path to the page so, instead of getting something like:

```
/home/vitor/datasets/unemployment.csv
```

You get:

```
C:\fakepath\unemployment.csv
```

To avoid bothering the user showing this ```fakepath``` stuff, we remove it,
showing just the file name. This only happens when uploading a file. The next
time you edit the resource, we'll have the entire URL, so that'll be shown
instead.
[#1550] Merge the merge and attached states into filled state

They're the same now.
[#1550] Refactor the state machine into a simpler architecture

We just have two states now, so we can simplify stuff.
[#1550] Initialize correctly the status of the image-upload
[#1550] Remove "Remove" button, as we now only use the "X" at the input
[#1550] Disable URL field when uploading image
[#1550] Remove unused "template" option

As far as I could see, this was never used. Maybe the structure of this code
came from copy/pasting from somewhere else where it made sense, and it was left
by mistake.
[#1550] Disable URL input if it belongs to an uploaded file
Merge pull request #1550 from ckan/1550-what-file-did-i-upload

[#1550] Show uploaded filename