Show GAS fee on real invocation confirmation dialogue

[deanpress]

Expected Behavior

Since invocations above 10 GAS are no longer free, users should be made aware of the fee when sending an invocation.

Current Behavior

The invocation dialogue is currently not displaying any fees when reviewing real invocations.

Possible Solution

Before sending a real invocation, the client should do a testinvoke, then display the fee information and the "expected output" retrieved from the test invocation in the invocation confirmation dialogue. In the case they fee is <=10 GAS, set displayed fee to "free". In the case it's >10 GAS, display total GAS fee - 10 as the displayed fee.

[jeroenptrs]

@deanpress one way would be to have a testinvoke go before an invoke, where you can see the calculated gas cost. However, we should test how this works with SC's using CheckWitness, as far as I can remember that might give incorrect results when it comes to testinvoke if addresses are badly formatted.

[DalderupMaurice]

I think this one can be generalized to the complex dialog wrapper? @mhuggins