UX improvements

[EwelinaSkrzypacz]

As this is the first time I have launched this project, I see some small things that could be improved.

• Page titles - title of the page is the link of the page I am currently on - I'd like to have real title, like "Studenci" or something like that.
• Tooltips - I didn't know that this check icon is for making the semester active/inactive. Adding some tooltip would be really helpful.

• Delete icon - I think that trash icon will be better.
• Add some sorting/filters on index views.
• Add missing translation in validation attribute (password, label, identifier); also we should translate name of icons in "Formy kontaktu"
• Confirmation dialog - instead of traditional confirmation dialog like we have now

it will be cool to have "undo" feature like Google Gmail provides

of at least button with action like "Usuń" should be black and "Anuluj" white

• Adding course to semester - if no course/semester exists, select looks like this:

[krzysztofrewak]

I would stay with current icons.