toggle pc hex <-> decimal

<a href="https://github.com/MrChico"><img src="https://avatars0.githubusercontent.com/u/8930559?v=4" align="left" width="96" height="96" hspace="10"></img></a> **Issue by [MrChico](https://github.com/MrChico)**
_Tuesday May 15, 2018 at 09:40 GMT_
_Originally opened as https://github.com/dapphub/dapp/issues/89_

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Would be a slick feature!
