[ANALYSIS] Improve data processing #2

For data with species with maximum longevity under 1 year, logarithm from their longevity will be negative.

• Shift all data +1 after log
• Save all real and predicted longevity
• Check and fix _ontology_plot
• Filter out clusters under threshold in Model.__init__
• Use --exclude 'Homo sapiens' 'Physeter macrocephalus' 'Balaenoptera physalus' 'Eschrichtius robustus'
• Improve plots for ontology - remove legend and add y title