deps: Context of deps declaration by techs

Right now we must write like this:
b__e_m_v.deps.js

``` js
{ tech: 'js', mustDeps: { tech: 'bemhtml', block: 'b', elem: 'e', mods: { m: 'v' } }  }
```

It's strange, because we already have BEM-item context and it's possible to write:

``` js
{ tech: 'js', mustDeps: { tech: 'bemhtml' }  }
```
