Add functionality to modify main address

[matt-auckland]

• Need a new api route on the back end to update the address.json file with the new address
• On the settings page we need a form to update the address
• On the deposit widget we need to a link to the settings page, something like: "Update wallet main address"
• When we click submit, we will force the user to enter their username and password
• once we get the potential new address on the backend, we will validate it with the RPC command validateaddress and check the JSON returned for isMine === true.
• If true then we will update the address.json file

To create the new component you can use the angularcli: ng g component settings/componentName

The form just needs a title, a field to enter the address and a submit button.

When we click submit we want a pop up to to appear that asks if the user is sure and the details are correct. If you need an example on how to do this see generic-rpc-form.component

We send address to the /updatemainaddress route and we will validate the address with the validateaddress rpc command before we update the address.

There is an example on how to update a file using nodejs in the /uipassword route