RFR: 8277756: DatePicker listener might not be added when using second constructor

[Marius Hanl]

The `valueProperty()` and `chronologyProperty()` listener are now added in the second constructor of `DatePicker` 
(`public DatePicker(LocalDate localDate)`) instead of the first one (`public DatePicker()`).
Therefore, both listener are now added no matter which constructor is used.

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Commit messages:
 - 8277756: DatePicker listener are now always added regardless of which constructor was used

Changes: https://git.openjdk.java.net/jfx/pull/801/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=801&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277756
  Stats: 116 lines in 2 files changed: 94 ins; 19 del; 3 mod
  Patch: https://git.openjdk.java.net/jfx/pull/801.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/801/head:pull/801

PR: https://git.openjdk.java.net/jfx/pull/801