Filesystem

This is still wip

# Tasks

* SpoonFile::exists gets replaced by BackendModel::getContainer()->get('filesystem')->exists
* SpoonFile::delete gets replaced by BackendModel::getContainer()->get('filesystem')->remove
* SpoonFile::move gets replaced by BackendModel::getContainer()->get('filesystem')->rename
* SpoonDirectory::exists gets replaced by BackendModel::getContainer()->get('filesystem')->exists
* SpoonDirectory::create gets replaced by BackendModel::getContainer()->get('filesystem')->mkdir