Untangle drush make

- Simplifies code a lot.
- Provides an addition to pm-download to specify project type along with the project name. Just add `/project-type` at the end of project name (and optionallly version).

```
drush dl date/module
drush dl drupal/core
drush dl drupal-7.23/core
```

- Drush make leverages this new feature of pm-download. To profit of this, makefiles must only add [type] key to projects. Two example makefiles:

```
api = 2
core = 7

projects[drupal][type] = core
projects[date][type] = module
```

```
api = 2
core = 7

defaults[projects][type] = module

projects[drupal][type] = core
projects[] = date
projects[] = token
```