Some eggs info in metrics

[ps1dr3x]

next_egg_hatching value is updated when the incubate_eggs worker checks the walked distance
hatched_eggs value is updated by the incubate_eggs worker when a egg hatches

[mention-bot]

@ps1dr3x, thanks for your PR! By analyzing the annotation information on this pull request, we identified @Kassadd, @rawgni and @Moonlight-Angel to be potential reviewers

[solderzzc]

CI failed
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ERROR: test_get_stats_line (tests.update_live_stats_test.UpdateLiveStatsTestCase)

Traceback (most recent call last):
File "/home/travis/build/PokemonGoF/PokemonGo-Bot/tests/update_live_stats_test.py", line 174, in test_get_stats_line
line = self.worker._get_stats_line(self.player_stats)
File "/home/travis/build/PokemonGoF/PokemonGo-Bot/pokemongo_bot/cell_workers/update_live_stats.py", line 253, in _get_stats_line
'next_egg_hatching': 'Next egg hatches in : {:.2f} km'.format(next_egg_hatching),

ValueError: Unknown format code 'f' for object of type 'str'

`