[10] Removal of Legacy Gateway/Bridge

This issue should be for removing the legacy Deposit/Withdraw section. Missing features on the Gateway/Bridge modal should be moved over to be implemented there instead.

Once done, everything connected to this section should be cleaned out.

Dedicated 10 hours for this task. Will hopefully be less.

### Features Missing
Do we have features on the Legacy Withdraw and Deposit page that the current modal can't handle?

- GDEX Requires a `Service Agreement`.
- GDEX has a "Recent Withdraw/Deposit" API
- This could be added as support on the "Account Dashboard" as a tab - "Gateway Transactions" for those that support this, currently only GDEX (?)
- Source: https://github.com/bitshares/bitshares-ui/blob/develop/app/components/DepositWithdraw/gdex/GdexHistory.jsx

* *Updated 2019-07-13: Missing Features List*

Start by reading app/components/DepositWithdraw/gdex/GdexHistory.jsx and tracing the legacy Deposit/Withdraw section and current Gateway/Bridge modal. Identify missing GDEX service-agreement and recent-transaction support, then verify that the replacement handles them and that the legacy section and connected code are removed.

Written by the indexing model from the issue text.