Code cleanup: ArchiveRecord + impl moved into same Scala file

[lintool]

What does this Pull Request do?

Cleans up code for ArchiveRecord and adds documentation.

• Per https://docs.scala-lang.org/style/control-structures.html - Omit braces if you have an else clause.
• Per https://docs.scala-lang.org/style/files.html - As a rule, files should contain a single logical compilation unit. By “logical” I mean a class, trait or object.
• Added documentation.

[ruebot]

Question about blank line. Other than that, looks good and I'll merge when TravisCI turns green.

[codecov]

Codecov Report

Merging #230 into master will increase coverage by 0.2%.
The diff coverage is 83.33%.

@@            Coverage Diff            @@
##           master     #230     +/-   ##
=========================================
+ Coverage   59.87%   60.07%   +0.2%     
=========================================
  Files          39       39             
  Lines         770      774      +4     
  Branches      137      137             
=========================================
+ Hits          461      465      +4     
  Misses        268      268             
  Partials       41       41

Impacted Files	Coverage Δ
...ain/scala/io/archivesunleashed/ArchiveRecord.scala	83.33% <83.33%> (ø)

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[ruebot]

Weird. My comment from earlier is missing.

...do we need this blank line?

[lintool]

I can't find Scala style guides that dictate import, but for Java, it is common to have groups separated by blank lines, see http://checkstyle.sourceforge.net/config_imports.html

To quote, one common approach is:

• group of static imports is on the top
• groups of non-static imports: "java" and "javax" packages first, then "org" and then all other imports
• imports will be sorted in the groups
• groups are separated by, at least, one blank line

[ruebot]

Ah, ok. That make sense. Let's just proceed with using that approach.

As an aside, I had the same problem trying to find guidelines on Scala style imports, and ended up doing it alphabetically, and soon realized order does matter at times. 🤷‍♂️