Use dedicated birthday entry controls (#67)

frontend/app/lib/l10n/en.arb

@@ -269,7 +269,11 @@
   "kycProfileHelp": "Enter your details exactly as shown on your identity document.",
   "kycFullName": "Full legal name",
   "kycBirth": "Date of birth",
-  "kycBirthHelp": "YYYY-MM-DD, for example 1990-04-23",
+  "kycBirthDay": "Day",
+  "kycBirthMonth": "Month",
+  "kycBirthYear": "Year",
+  "kycBirthInvalid": "Enter a valid date of birth.",
+  "kycBirthFuture": "Date of birth cannot be in the future.",
   "kycCountry": "Country of residence",
   "kycCountrySelect": "Select a country",
   "kycCountrySearch": "Search countries",