Add toString method to the Params class

[tgrall]

• As I am looking at CSC implementation I think it is interesting to add this method.
• I have not added any test as it is very basic update, let me know if I need to

[sazzad16]

Params may contain byte[]. This solution does not handle this.

[tgrall]

@sazzad16 thanks for your review.

I have updated the PR with the following:

• replace the simple Map.toString() using a List (that is closer to how params are used by applications)
• manage byte[]
• add a simple test