Compare dataframe classes

[gowerc]

Closes #42

This one was a little more involved so a couple of points to bear in mind below:

• I currently create a "summary" dataframe which contains the number of rows and columns as well as the class of each dataset. I wanted this summary to appear at the top of the printed output regardless of wether users wanted to check the class as its a nice high level summary. This thus requires some special case handling in the main diffdf function to adjust the corresponding issue. e.g. if the check is disabled and there aren't any other issues then remove the summary issue as it should be regarded as compared the same. Likewise the warning message needs to be different to the actual display string. (happy to talk about this more if the special case handling doesn't make sense

• In general this highlights to me that our current issues setup is too rigid and needs to be overhauled to handle more dynamic content (e.g. display content that isn't strictly to be regarded as an issue). I didn't want to do this overhaul here as that would be too much for a single PR so have just added special case handling logic instead.

• The printed output for this looked clunky so I played around with the newlines and spacings to try and make it look as good as I think I can get it (thus some of the print snapshots have changed slightly)

• A slightly bigger change to the printed output is I took this moment to remove the "all rows are show below" as this is an utter waste of space

• I also removed the "a summary is shown below" as it no longer makes sense when combined with the summary table

• The unit tests for row_print where too fragile and broke despite only white space changes so I reworked them to be a little bit more robust by making them relative to each other rather than testing for specific row lengths (e.g. show that changing row_limit from 5 to 10 increases the number of lines by 5)

[github-actions]

Code Coverage Summary

Filename                Stmts    Miss  Cover    Missing
--------------------  -------  ------  -------  --------------------------
R/ascii_tables.R          105       8  92.38%   10, 148, 158, 163-166, 211
R/cast_variables.R         49       0  100.00%
R/diffdf.R                159      18  88.68%   323-340, 367
R/generate_keyname.R       10       1  90.00%   16
R/identify.R              134       9  93.28%   246, 283-290
R/is_different.R           52       0  100.00%
R/issuerows.R              40       0  100.00%
R/issues.R                 17       1  94.12%   51
R/misc_functions.R         34       2  94.12%   9, 13
R/print.R                  20       0  100.00%
TOTAL                     620      39  93.71%

Results for commit: c30e97f

Minimum allowed coverage is 80%

♻️ This comment has been updated with latest results

[github-actions]

Unit Tests Summary

  1 files   11 suites   5s ⏱️
 43 tests  42 ✅ 1 💤 0 ❌
560 runs  556 ✅ 4 💤 0 ❌

Results for commit c30e97f.

♻️ This comment has been updated with latest results.