Make all path a "Path"

[hcabel]

The Path class will be our abstract layer for all path in the engine. It need to have a couple of feature:

• [x] by default use / has delimiter
• [ ] convert to windows path easily
• [ ] Append using + operator
• [ ] Get the the target of a path (/A/B/c.png = c.png)
• [ ] Get the file name into a full path (/A/B/c.png = c)
• [ ] Get the file extension of a full path (/A/B/c.png = png)

then is a matter or casting all the path to this class