fix: fix build failures after sprint 2

[thanhpd]

1. Updated string.xml to fix error in screenshot 1 (src\main\res\values\strings.xml)
2. Updated build.gradle to fix error in screenshot 2 (src\main\res\layout\fragment_runs_stat.xml)
3. Updated src\main\java\de\dennisguse\opentracks\stats\TrackStatisticsUpdater.java to fix error in screenshot 3
4. Commented out code in src/main/java/de/dennisguse/opentracks/ui/aggregatedStatistics/SeasonStats/RunAndChairStatActivity.java and src/main/java/de/dennisguse/opentracks/ui/aggregatedStatistics/SeasonStats/SeasonStatActivity.java to fix error in screenshot 4
5. Commented out code in src/main/java/de/dennisguse/opentracks/ui/aggregatedStatistics/AggregatedStatisticsAdapter.java to fix error in screenshot 5