Datas does not gather well when yearly period time is defined

[MathieuMaes182]

It appears that when using the yearly period time format, datas are still displayed according to their months.

I've been creating a PR that fix the problem:

• by setting month and day to 1 and 1 by default if you choose the yearly period (those ones are not relevant when datas are displayed by years)
• and by using the DATE_FORMAT doctrine function (instead of DATE) (need to be import by the user in his doctrine.yaml file). The date format is passed as a parameter of the query builder. I've defined the three formats in the DataFetcher\Data class as constants, and created a function that returns the format according to what it receives in the configuration.

The two screenshots here shows how the plugin is working now:

And here find how it works with the fixes:

Here is the link to the PR: #23

I remain available here to answer any questions or to discuss the choices I've made.