RFR: 8268642: Expand the javafx.beans.property.Property documentation [v2]

[Michael Strauß]

> * Expand the `Property.bind` and `Property.bindBidirectional` documentation
> * Change the name of the formal parameter of `Property.bind` to "source" (currently, it is inconsistently named "observable", "rawObservable" or "newObservable")

Michael Strauß has updated the pull request incrementally with one additional commit since the last revision:

  changes as per review

-------------

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/533/files
  - new: https://git.openjdk.java.net/jfx/pull/533/files/db112677..ea1bf776

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=533&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=533&range=00-01

  Stats: 70 lines in 11 files changed: 20 ins; 26 del; 24 mod
  Patch: https://git.openjdk.java.net/jfx/pull/533.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/533/head:pull/533

PR: https://git.openjdk.java.net/jfx/pull/533