Implement recommended staking amount

[sihoang]

Rationale: We would like to prefill the stake amount so that users just need to Select a cause and click Stake Now. Let's call the minimum amount required is A

For those that never have any stakes, any amount will get their rank from N/A to a number. Therefore, we will prefill the minimum amount A in this case.

For those that have a rank i.e. had been staked before, the recommended amount will be the greater of:

• minimum amount A
• amount that can increase the cause's rank by 1

Any thoughts on the minimum amount would be?

[sihoang]

@gliinbox @modernbuddha This might be related to our fee model. Just want to get your final call on the value of A (the prefilled amount). For now, I put 100 TRST.

[gliinbox]

let's start with 100 TRST -- we can then change later when fee model is more developed