Front-end validation

In consentForm:
- Summing up percent to 100
- Fields in form are required now
- Field with ojsId is readonly now
- Changed managing buttons in form (visually looks better)
- Added sample Financial Disclosure text

In index (page before consent form):
- field is required now
- added verification of input (checks if value is numeric)

Note: tooltips displaying when required field is not filled are in polish, cause bootstrap uses web browser language

I'll deploy it on zeuko-io-article-manager.herokuapp.com when SBT start to cooperate. :)