[Converter] Created ContentConverter

* removed `Filesystem`'s `detectLineBreak` method
* removed `File`'s `readlines` and `writelines` methods
* injected `LineContentConverter` into:
  + `LineReplaceStrategy`
  + `LineSearchStrategy`
  + `LineNumberSearchStrategy`
* added `LineContentConverter`
* added `ContentConverter`
[FactoryMethod] Created new ones

* added `Line` factory method for empty ones
* added `Filesystem` factory method to force creation
* moved factory methods into `Gnugat\Redaktilo`
[Replace] Fixed `Editor::addAfter`

The cursor wans't moved down to the new line.
[Replace] added BundleRouting example

Allows to make sure line insertions is done tyhe right way.
[DocConverter] Updated the doc
[DocConveret] Created complete reference guide
[DocConverter] Created a tutorial
[0.7] Updated CHANGELOG
Merge branch 'doc/converter'