More flexible package installer

This PR will enable more flexible structure in packages.

Currently only the following is allowed:

> package.zip/package
> package.zip/package/Controller
> package.zip/manifest.json

This PR will allow additional structures such as:

> package.zip/Subfolder/package
> package.zip/Subfolder/package/Controller
> package.zip/Subfolder/manifest.json


> package.zip/Subfolder/Controller
> package.zip/Subfolder/manifest.json


> package.zip/Controller
> package.zip/manifest.json

In simple words it drops the requirement for the "package" subfolder and enables Model+View+Controller folders to reside in the same directory as manifest.json.

Another advantage is that the whole package could reside in a subfolder which will allow installing zipped-up repositories straight from Github.

Tested with php 5.5 on Win 7 and Ubuntu 12.04
How do you see this?