Prusa i4 upgrades

This is a set of updates dedicated for so called 'Prusa i4' 3D printers. As I've received my printer with few broken parts (y-axis, left vertical panel broken around electricity slot) I had to design several replacement parts.
Later I made some enhancements for filament (both guide and holder) as the native was unreliable. It was made in connection to extruder locks (it lacked a power to pull a filament resulting in empty layers).
X-axis was a problem all the time, making layer shifts far too often. I have find out that bed's bottom left corner was going down too much, so I've designed a support based on additional rail. I was forced to bath all of the X-rail bearing balls and the bearing itself in the oil, as there was a lot of rust inside.
Once, in one and warm beautiful day, the relay broke up (the one empowering the bed) I was forced do design a better cooling system for the inside of the printer.

In general post of those parts can be updated to be better and has their small