OpenweatherMap: Localized item names

[marcinczeczko]

I'd like to propose changes that allows to generate item labels localised to the current language.

• The problem I had was the unicode characters especially for day names generated by calendar module
• The I wanted to customise those labels to use values such as Tomorrow, Day after tommorrow (in PL language), etc.
• There is corresponding PR Enable unicode character handling without the hassle #356 that also fixes items core lib so the unicode labels are gracefully handled.
• Names of the items are fully localized using MAP transformation service