Test's random name gen now uses uuid4

This test used a random integer to generate the name of a file.  Although
it doesn't pose a real problem, it's probably better just to drop a UUID
in instead of a 3-digit number, to avoid collisions.

Partially implements blueprint: selenium-integration-testing

Change-Id: I95fd2c25dc4e2e5ddc47cd390b472c8ee2310e97
Closes-Bug: 1399219
Integration tests - 3 new form fields

I added 3 new form fields, that are frequently used
in different horizon's forms:
* CheckBoxFormField - with the options to mark, unmark
and check if already marked.
* ChooseFileField - with a choose file action.
* TextAreaFormField - intended for multi-line text input box.

The reason I separated this change from the Images page patch
is to allow others to use it in their patches without forcing
the images as a dependency.

Partially implements blueprint: selenium-integration-testing

Change-Id: I94260db6089e44e66bf19b0ede172eec1756cdc5
Merge "Integration tests - 3 new form fields"
Merge "Test's random name gen now uses uuid4"