Change typing rate table to account for reads mapped to multiple markers at the same locus

[agshumate]

This PR closes #171 . Now that we allow multiple marker definitions at a given locus, reads are typed multiple times. This PR changes the table in the report to show Attempted Typing Events and Successful Typing Events where a "typing event" is defined as haplotype calling for 1 read at a single marker definition.

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• [x] Changes are clearly described above
• [x] Any relevant issue threads are referenced in the description
• [x] Any new features are tested (see the development manual for details)
• [x] CLI documentation (see docs/cli.md) and Python API documentation (see microhapulator/api.py) are up-to-date and in sync
• [x] Substantial changes are documented in CHANGELOG.md (see https://keepachangelog.com/en/1.0.0/)