"Current balance" column in User management view

[lucyhilltop]

• Change "N balance" title to "Current balance".
• Instead of showing days left over from N year, show the current balance of vacation days for user (i.e. the days the user has already earned).
• Next to the current balance nr show an (i) icon.
• When user hovers on the balance nr or the icon show the following on a tooltip:

Current remaining days paid vacation: 14 study leave: 30 ---------------------------- Balances from previous years 2017: 17 2016: 14 2015: 28 ...

• The same should be done in User management user detail view