[proposal] Rewrite site modules system to use composer

[seyfer]

Submodule system is awful. All going good until you need remove submodule..

To remove a submodule you need to:

Delete the relevant section from the .gitmodules file.
Stage the .gitmodules changes git add .gitmodules
Delete the relevant section from .git/config.
Run git rm --cached path_to_submodule (no trailing slash).
Run rm -rf .git/modules/path_to_submodule
Commit git commit -m "Removed submodule <name>"
Delete the now untracked submodule files
rm -rf path_to_submodule

And all other not standard adding operations became git conflict and problem hell.

Composer is better modern solution. You can just host composer.json for each branch with required modules list and build site on it.

And more important - it will force developers to add composer.json and add packets to packagist.

Kohana 3.4 will implement composer installation too by default.