Create a splitCoins function

[Tzal3x]

In this current version 2.0.7 the library requires that the user has already split the coins into multiple ones so that workers can be created from them.

In order for the library to be plug n' play, this process should be done through the library without making the user think how to do it.

Ideally we should provide a function like splitCoins or generateCoins. The core functionality is already implemented in setupTestsHelper.addNewCoinToAccount but it is only used for the setup of tests.

[Tzal3x]

After a short discussion with the team we decided that coin splitting is not the library's responsibility.