Made some changes to ojo_parse_county and added ojo_list_counties

[andrewjbe]

Changes to ojo_parse_county():

• squish argument is now consistent regardless of other args; if TRUE, there will be no spaces, and if FALSE, all spaces will remain. I also altered the tests slightly to reflect the changed behavior.
• suffix argument is now a real thing; it adds the argument to the county names and respects all other args

New ojo_list_counties() function:

• Returns all 77 county names in lowercase by default, as a tibble with one col "value" to match the other ojo_list_ functions.
• Also includes case, squish, suffix args from ojo_parse_county(), so you can pass those arguments along easily to get a formatted list.
• Also includes oscn_only arg; if TRUE, will filter the list to only include the 13 oscn counties.

[andrewjbe]

I was creating a UCCS code lookup table for a different project, and I figured it would be handy to have the script I used in /inst here. I also included the resulting dataset of unique charge descriptions; let me know if there's a better spot for it.