Optionally print project path in table notes annotation

[kylebaron]

Summary

• Retain the current behavior of writing the name of the output file into the table annotation
• As noted in the attached vignette, the big change here is ability to add both the output file name and output path (directory) into the table annotation; this means we need to lock in the final location for the table as we build the table; the vignette shows this.
• tab_notes() gains the following arguments
  • output_dir where (what directory) to save the file; respects pmtables.dir
  • path.type how to render output_dir in the annotation;
  • See implementation details
• New function: format_table_path(); does equivalent of what we already do in mrggsave

Current default

Currently, we can take in the output file name and that gets
included in a table note. However, the decision about where
to save that file is deferred until we actually call
stable_save().

The changes to pmtables include accepting the output file path
when we create the table. Now, if the user passes the output path
and it is included in the table annotation, we have to respect that
information when saving; it can't be changed after the annotation
is created.

Implementation detail

Currently, it is the tab_notes() function that handles all the
arguments for R source file, output file, output directory etc. But
this is a but of a misnomer now, because the function doing more
than just writing a note and saving the file name for later; real
decisions about output file locations are being made.

I have added a non-exported function tab_files() that handles
all the file / path manipulation and arguments that get passed
to tab_notes() eventually go to tab_files(). In the future,
I will open up tab_files() since that more accurately reflects
where the file / path proecessing is taking place.

source-path.pdf

[kyleam]

I'll interactively test this a bit, but this is looking good to me aside from my minor comments above.

[KatherineKayMRG]

From a user perspective, this worked well for me on the project and I like the opt in approach. I'll leave the more thorough code review to @kyleam

[kyleam]

LGTM aside from typos mentioned above

[kylebaron]

Thanks, @kyleam ; working on the typos now.