Improve roxygen documentation

[RasmusSkytte]

Intent

This PR takes a thorough look at the roxygen documentation and aligns the style internally and with the mlr3 style.
(This fixes the param_and_field_linter() lints we have been getting since merging PR #102)

In addition, some use of the db_table_id argument have been renamed to db_table to align names of arguments across functions.
The recent updates to id(), means that there we no longer need to supply an Id but just something coercible by id().

There also was some imports libraries that was causing issues. I removed these from imports and instead ensured every function call was visibly binded.
This also meant we could have fewer dependencies and move some dependencies to "Suggests" and not rely on these.

Approach

• Argument db_table_id renamed to db_table.

Roxygen docs:

• Datatypes of arguments have been made explicit by adding the specification (`<datatype>()`)\cr to all function args.

• The indentation of roxygen docs have been aligned across functions

• The order of roxygen tags have been aligned (but is not actively enforced)

  • title
  • description
  • param
  • return
  • examples
  • imports
  • export

• Punctuation marks added throughout.

• Examples made conditional on the installation status of RSQLite.
  This mean that with a few more changes, we could move RSQLite to "Suggests" and don't have it as a dependency.

Known issues

N/A

Checklist

• The PR passes all local unit tests
• I have documented any new features introduced
• If the PR adds a new feature, please add an entry in NEWS.md
• A reviewer is assigned to this PR

[LasseEngboChr]

Lots of small adjustments to align the style :-)
Only a couple of suggestions.

[RasmusSkytte]

Fixes #69