An interactive gii console command

This a rework of pull request #2789 introducing a gii command line tool that works interactive. Fixes #1280

- extensions/gii/commands/GiiController is the initial idea implemented by @schmunk42
- extensions/gii/commands/InteractiveController is a draft of how I think gii should work on the command line

It is listed in the command list when gii is installed:

![screenshot-2014-07-14t17 16 35](https://cloud.githubusercontent.com/assets/189796/3572644/0de349a6-0b6a-11e4-8574-514ba877cd91.png)

Running it without a generator, lets you select first, running `./yii gii/interactive model` will diretctly run the model generator.

![screenshot-2014-07-14t17 19 03](https://cloud.githubusercontent.com/assets/189796/3572659/38451ea4-0b6a-11e4-8cc1-c8ae9062378e.png)

When running you are asked to fill models attributes including validation:

![screenshot-2014-07-14t17 21 58](https://cloud.githubusercontent.com/assets/189796/3572727/bb23ac82-0b6a-11e4-8be6-f3ac06fd16fe.png)