baseapp: Allow alphanumerics in routes

[ValarDragon]

Previously only alphabetic characters were allowed.

Closes #1587

• Updated all relevant documentation (docs/) - current docs are correct
• Updated all relevant code comments
• Wrote tests - numeric usage is already covered in a test vector
• Updated CHANGELOG.md
• Updated cmd/gaia and examples/

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #1705 into develop will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff            @@
##           develop    #1705   +/-   ##
========================================
  Coverage    62.35%   62.35%           
========================================
  Files          120      120           
  Lines         7119     7119           
========================================
  Hits          4439     4439           
  Misses        2429     2429           
  Partials       251      251

[cwgoes]

utACK