Change network in wallet

[oanamangiurea]

Adding the ability for the user to change the wallet network, from mainnet to ropsten testnet.

1. Dropdown to appear in menu https://projects.invisionapp.com/d/main#/console/15222689/316491950/preview with tooltip. TBD: CS to create page in help center with explanation on what testnet is.

2. Marketplace applications will be unavailable on the test network. While we will allow for browsing, if a user tries to access any service, the following modal will appear: https://projects.invisionapp.com/d/main#/console/15222689/375455584/preview

[oanamangiurea]

@vitalikda need your support please with a little help center text. As stated above, we'll need to describe what is a testnet, and the difference from mainnet. We are using Ropsten as testnet.

I've got the following 2 descriptions from the web, just need it in our own words. Thank you!

The testnet- short for test network – is an exact replica of the original blockchain, with the same technology, software, and functionalities. The only difference is that transactions on the testnet are simulated (or ‘fake’) and the coins in the testnet does not possess any real value outside of the testnet environment.

The testnet is an alternative Bitcoin or Ethereum block chain, to be used for testing. Testnet coins are separate and distinct from actual coins, and are never supposed to have any value. This allows application developers or bitcoin testers to experiment, without having to use real bitcoins or worrying about breaking the main bitcoin or ethereum chain.