Bug#862529: uncommons-watchmaker-doc: Rename the documentation package to lib*-java-doc

[殷啟聰]

The reason behind this package name is that it provides the Javadoc
for both of the 2 library packages
(libuncommons-watchmaker-framework-java &
libuncommons-watchmaker-swing-java). If I split their Javadocs, there
will be dead hyperlinks (or in fact the class fullname instead of
hyperlinks) throughout the Javadoc of
libuncommons-watchmaker-swing-java.

pkg:gradle-doc follows the same reason, I guess. Besides, I fail to
find a javadoc package naming rule in the current Debian Java Policy.

The popcon is indeed low because it was merely meant for
stc:android-toolchian-jack [1]. But now that Google has officially
obsoleted this tool...

[1]: https://bugs.debian.org/847427