`R CMD CHECK` fails on `v2.3`

Due to broken vignettes and examples that still use connect_to_etn():

[ ] #306
[x] #308
[x] formattable suggested but not available
[x] unable to verify current time on VLIZ RStudio
[x] Examples download_acoustic_dataset() #308
[x] argument documentation get_tags()
[x] Examples get_acoustic_deployments() #308
[x] if condition comparing class to string: etn/R/list_values.R

checking R code for possible problems ... NOTE
  Found if() conditions comparing class() to string:
  File ‘etn/R/list_values.R’: if (class(arguments$column) == "name") ...
  Use inherits() (or maybe is()) instead.



N  checking package dependencies (5.9s)
   Package suggested but not available for checking: ‘formattable’
N  checking for future file timestamps (4m 0.7s)
   unable to verify current time
N  checking Rd line widths ... NOTE
   Rd file 'download_acoustic_dataset.Rd':
     \examples lines wider than 100 characters:
        #> * included acoustic projects:  albert, Apelafico, bpns, JJ_Belwind, leopold, MOBEIA, pc4c, SPAWNSEIS, ws2, zeeschelde

   These lines will be truncated in the PDF manual.
W  checking Rd \usage sections ...
   Undocumented arguments in documentation object 'get_tags'
     ‘api’

   Functions with \usage entries need to have the appropriate \alias
   entries, and all their arguments documented.
   The \usage entries must correspond to syntactically valid R code.
   See chapter ‘Writing R documentation files’ in the ‘Writing R
   Extensions’ manual.
E  checking examples (731ms)
   Running examples in ‘etn-Ex.R’ failed
   The error most likely occurred in:

   > base::assign(".ptime", proc.time(), pos = "CheckExEnv")
   > ### Name: get_acoustic_deployments
   > ### Title: Get acoustic deployment data
   > ### Aliases: get_acoustic_deployments
   > 
   > ### ** Examples
   > 
   > # Set default connection variable
   > con <- connect_to_etn()
   Error in connect_to_etn() : could not find function "connect_to_etn"
   Execution halted

❯ checking examples ... ERROR
  Running examples in ‘etn-Ex.R’ failed
  The error most likely occurred in:

  > base::assign(".ptime", proc.time(), pos = "CheckExEnv")
  > ### Name: get_acoustic_deployments
  > ### Title: Get acoustic deployment data
  > ### Aliases: get_acoustic_deployments
  > 
  > ### ** Examples
  > 
  > # Set default connection variable
  > con <- connect_to_etn()
  Error in connect_to_etn() : could not find function "connect_to_etn"
  Execution halted

❯ checking Rd \usage sections ... WARNING
  Undocumented arguments in documentation object 'get_tags'
    ‘api’

  Functions with \usage entries need to have the appropriate \alias
  entries, and all their arguments documented.
  The \usage entries must correspond to syntactically valid R code.
  See chapter ‘Writing R documentation files’ in the ‘Writing R
  Extensions’ manual.

❯ checking package dependencies ... NOTE
  Package suggested but not available for checking: ‘formattable’

❯ checking for future file timestamps ... NOTE
  unable to verify current time

❯ checking Rd line widths ... NOTE
  Rd file 'download_acoustic_dataset.Rd':
    \examples lines wider than 100 characters:
       #> * included acoustic projects:  albert, Apelafico, bpns, JJ_Belwind, leopold, MOBEIA, pc4c, SPAWNSEIS, ws2, zeeschelde

  These lines will be truncated in the PDF manual.

1 error ✖ | 2 warnings ✖ | 3 notes ✖
Error: R CMD check found ERRORs
Execution halted

Exited with status 1.

inbo / etn

`R CMD CHECK` fails on `v2.3` #307