Interact update issues

There are some lingering issues with the interact update:

- [x] the slider is now wider by default, which makes the default textbox width look too narrow.  Compare:

```python
@interact
def f(n=(0,1), y=x^2):
    print n,y
```
- [x] the function name isn't defined the first time the function is run, so this gives an error:

```python
@interact
def f(n=(0,1)):
    print f.n
```

- [x] dynamically added controls don't respect an update button:

```python
@interact
def f(n=(0,1), auto_update=False, **kwargs):
    print n, kwargs    
f.x=1 # the control for x doesn't wait for the update button to be pressed
f._update()
```

- [x] http://www.math.ualberta.ca/~novoseltsev/2013Winter215Q1/VC01_vector_fields_public.html doesn't work anymore

- [x] fix (possibly correct): 0f4d5e8056393717b49daaa9199c76230c8fc921 Changes to the adapter functions mean this doesn't work (I think it used to work):

```python
def to_value(l):
    return map(SR, map(str, l[0]))
@interact
def _(      tuv=input_grid(1,6, label=r"$tuv$-limits:", default=[0, 4*pi, 0, 2*pi, -1, 1], width=6, to_value=to_value)):
    print tuv    
```

- [ ] The `._changed` attribute is incorrect in this situation:

```python
changed=[]

@interact
def f(self, n=(0,1), **kwargs):
    global changed
    changed.append(self._changed)
    print changed
    if len(changed)<2:
        self.x=4
        self._update()
```

- [ ] This isn't a regression, but a request feature from the webwork folks: something like a f._save_state() that gives back a dictionary of control values and f._restore_state() that would take the dict and restore the state of the controls and update the function.  This also enables us to make 'bookmarks' of control settings.