[#651] Remove Client Methods

Description

The following to functions defined in the type class 'HasTezos` client have been removed from the type class together with their implementations.

• getTezosClient: only implemented for TezosClient.Impl but never used inside morley (dead code)
• importKey: only implemented once and used twice (once in tests), where also the the explicit implementation of TezosClient.Impl could be used.

Appart from that 3b2ac570 replaces haddock comments in inappropriate places have been with ordinary haskell comments.

Related issue(s)

• Fixed #651 (closed) .
• getAlias could not be removed as the requied feature in tezos has not been addressed yet. See tezos/tezos#836

Resolves #

✅ Checklist for your Merge Request

Related changes (conditional)

• Tests (see short guidelines)

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.

• Documentation

  • I checked whether I should update the docs and did so if necessary:
    • Root README and other README.md files
    • Haddock
    • docs/
  • I updated changelog files of all affected packages released to Hackage if my changes are externally visible.

Stylistic guide (mandatory)

• My commits comply with the following policy.
• My code complies with the style guide.