Merge cardano-wallet-launcher into cardano-wallet

[KtorZ]

Context

We currently maintain two separate executables as we historically needed to have a separate
process for launching and monitoring both the wallet server and its backend node. It was recently agreed with Daedalus' team that in the long run, Daedalus will be managing both processes itself and would only require the wallet to take care of itself.

Decision

• Moving towards this direction, we agreed on making the launcher a command of the cardano-wallet CLI instead of a new executable. This will make the support of multiple target backend slightly easier (having to maintain ultimately 3 executables instead of 6, and having the ability to simply remove the launcher command once Daedalus takes care of these bits).

• Friendly reminder to also update the .travis.yml file to make sure we adjust the build artifacts on releases.

Acceptance Criteria

1. cardano-wallet must have a new command launcher doing what cardano-wallet-launcher currently does
2. cardano-wallet-launcher mustn't exist anymore

---

Development Plan

• Create a new launch command in cardano-wallet
• Remove everything related to cardano-wallet-launcher
• Replace tests to use cardano-wallet launcher instead of cardano-wallet-launcher
• Review port validation (see Parameters --port and --bridge-port not validated correctly by CLI #422)

PR

Number	Base
#414	master
#422	master

QA

• There's no more cardano-wallet-launcher but a new launch command on cardano-wallet. Various tests and documentation bits have been updated to reflect that new setup.

• There was some issues with the --port validation also fixed as part of this ticket (with corresponding tests at both the cli-level and the unit level).

[jonathanknowles]

@KtorZ

cardano-wallet must have a new command launcher doing what cardano-wallet-launcher currently does

If commands are verbs, the perhaps we should call this command cardano-wallet launch?

[piotr-iohk]

lgtm