Clean up error messages on contract execution

[Endogen]

This is how a normal error message looks like if some assert is triggered in a contract

Since it's always an Assert, the structure of the error message is always the same. To make it not so techy looking, i propose to extract the error message itself and only show that. In the provided example it would then only show "Not optics to claim" (which is a pretty funny error message actually lol).

[JeffWScott]

assigned to @Dapiguabc