[Form][WebProfiler] Empty form names fix

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none

When a Form had no name, the markup was broken in the profiler, making the form tree ugly. This pull request changes the output so that `(no name)` string is displayed when no form name was available.

Before:
![screenshot 2014-10-21 00 06 23](https://cloud.githubusercontent.com/assets/345754/4706329/d596a3ec-5883-11e4-8c67-44a7f357f3e1.png)

After:
![screenshot 2014-10-21 00 08 02](https://cloud.githubusercontent.com/assets/345754/4706359/122674c2-5884-11e4-8237-0177a590f2a0.png)

Why not simply:
```jinja
{{ name|default('(no name)') }}