* Add networks tab to settings, with header.
* Adds network list to settings network tab.
* Adds form to settings networks tab and connects it to network list.
* Network tab: form adding and editing working
* Settings network form properly handles input errors
* Add translations for settings network form
* Clean up styles of settings network tab.
* Add popup-view styles and behaviour to settings network tab.
* Fix save button on settings network form
* Adds 'Add Network' button and addMode to settings networks tab
* Lint fix for settings networks tab addition
* Fix navigation in settings networks tab.
* Editing an rpcurl in networks tab does not create new network, just changes rpc of old
* Fix layout of settings tabs other than network
* Networks dropdown 'Custom Rpc' item links to networks tab in settings.
* Update settings sidebar networks subheader.
* Make networks tab buttons width consistent with input widths in extension view.
* Fix settings screen subheader height in popup view
* Fix height of add networks button in popup view
* Add optional label to chainId and symbol form labels in networks setting tab
* Style fixes for networks tab headers
* Add ability to customize block explorer used by custom rpc
* Stylistic improvements+fixes to custom rpc form.
* Hide cancel button.
* Highlight and show network form of provider by default.
* Standardize network subheader name to 'Networks'
* Update e2e tests for new settings network form
* Update unit tests for new rpcPrefs prop
* Extract blockexplorer url construction into method.
* Fix broken styles on non-network tabs in popup mode
* Fix block explorer url links for cases when provider in state has not been updated.
* Fix vertical spacing of network form
* Don't allow click of save button on network form if nothing has changed
* Ensure add network button is shown in popup view
* Lint fix for networks tab
* Fix block explorer url preference setting.
* Fix e2e tests for custom blockexplorer in account details modal changes.
* Update integration test states to include frequentRpcList property
* Fix some capitalizations in en/messages.json
* Remove some console.logs added during custom rpc form work
* Fix external account link text and url for modal and dropdown.
* Documentation, url validation, proptype required additions and lint fixes on network tab and form.
Ropsten links will still not work until Etherscan publishes their ropsten link format.
At that time we will need to update ui/lib/account-link.js
Otherwise, fixes#831
