gui: Implement consolidateunspent wizard

[jamescowens]

This implements a three step wizard that leads the user through the process of selecting inputs, selecting a destination, and
then reviewing the overall transaction.

Select Inputs:

The select inputs screen uses similar code to that in coincontroldialog to support the consolidate button there. Pointers to the coincontrol data structures constructed in sendcoinsdialog are passed into both coincontrol and the consolidateunspentwizard to faciliate using the underlying machinery in a unified manner. This is possible because both coincontrol and onsolidateunspendwizard are called with the sendcoinsdialog and are modal.

Note that there is a stop sign and the next button is disabled if more than 600 outputs are selected. The next button is also disabled if less than 2 outputs are selected (as it makes no sense to consolidate when there is no consolidation achievable based on the selection). If a filter operation is applied based on the filter criteria, and that criteria would result in more than 600 inputs being selected, the selection is reduced to 600 inputs and a warning triangle is presented.

Select Destination Address:

If all of the inputs selected in the prior page are from one address, then that address will already be preselected (but allow the opportunity for it to be changed by the user prior to pressing next). If the inputs selected correspond to more than one address, an address will NOT be pre-selected, and the user will be required to pick an address to proceed. The next button will be disabled until a valid address is selected for the destination.

Confirmation:

The final screen presents the details of the intended transaction for review by the user. When the "Finish" button is pressed, the transaction to send is filled in in the send dialog sreen, and the user can review the details again if desired and press the send button to send.

NOTE: I know the appearance needs to be fine-tuned. I am not necessarily the best at making pretty things UI-wise, but the basics are here. I also think we can move the Consolidate Wizard button out of the coincontrol frame, so that it is visible whether or not the advanced coin control is enabled in the config.

This further addresses #1984.

[jamescowens]

For some devilish reason the table widget on the select destination page shows numbers for the headers instead of the column labels. I have no idea why. The similar table widget in the consolidate button in coincontrol displays correctly. I am having @iFoggz see if he can find what I must be missing. I am marking it ready for review anyway.

@cyrossignol I am having you review this, since you were looking at the coincontrol code earlier and also just put up a complimentary PR. I think we should show the consolidate wizard button irrespective of the new "toggle" mode you implemented in #2126. We may want to favor this wizard in place of the consolidate button in coincontrol itself.

Since this wizard actually works with the underlying data structures in the coin control/send dialog, it can be used instead of, or partially or completely (pressing finish), and then go to coin control to make further adjustments, although this wizard exposes the subset of coin control functionality needed just for consolidation purposes.

[jamescowens]

The header problem is fixed. @iFoggz found it. I was using ui->addressTableWidget->clear(), instead of ui->addressTableWidget->clearContents() in SetAddressList!

[cyrossignol]

Some initial comments to start. Will circle back when I have time to do more thorough testing.

[jamescowens]

I think this now works the way I had intended. If you cancel out of the wizard after having selected inputs, you will now see they are correctly set in the coin control label fields (this was not working quite correctly before), and you can go to coincontrol and make further adjustments (this WAS working correctly). If you go back to the wizard, state is maintained, and you can pick up where you left off there if you choose.

The select destination address page in the wizard is now a bit smarter than the consolidate button in coincontrol. I think I need to retrofit the improvements from the select destination page to there.