Add a few options in all the charts

[giorgiouboldi]

What about adding a few very useful options in all the charts such as:

• font size options for labels and thicks
• Decimals places control
• Legends ON by default

Check latest custom chart by @fenicento that adopts this rules

[mikima]

Font size could be tricky, in some charts we have predefined styles, so we should ovverride the size per style
Decimals places control: do you have suggestion on how to handle it?
Legends probably must be updated chart by chart