Add the ability for free shipping based on cart total price, on opencart's default weight based shipping.

There are 2 default plugins on opencart. One for weight based shipping, and one for free shipping.
Free shipping plugin, has the ability to be enabled when cart total reaches the price we have set. But weight based shipping has not this option.
Actually, you have to enable both modules to be able to have weight based shipping and free shipping over x total.
In this case, customer will see 2 shipping methods, 1 free shipping, 1 with price (weight based shipping).

This module solves that issue, adds the ability for free shipping when total exceeds the price we set on weight based shipping.

To install:
1. Go to extensions>install and upload ocmod file.
2. Go to extensions>modification and press the modification button on top-right refresh button.
3. Go to shipping methods and open weight based shipping, there is an minimum price input for free shipping.