tarantula x carriage

###26-8-2017:
NEW:
* Fan clips added for holding the fans

###25-8-2017:
Started printing these files and bumped at some troubles..
* Chain holder changed, the placer broke with the old one and the belt holder bumped at the bolt of the y carriage.
* Stock hotend holders had some misplaced holes.

NEW :-)
* Added a dual fan mount stock hotend holder

###First version:
* Remix of the modular x carriage for a 2020 rail