gradle jdk build

[aanno]

I updated gradle (wrapper) to 6.8.2 and tried to improve the build on jdk a bit. However, I'm not an android developer and it is possible that I have broken something with android.

1. Provide a (maven) group for timeago and ta_library from gradle.properties
2. Provide the version for timeago and ta_library from gradle.properties
3. Pack a generated pom.xml with both jars (the way it would be if the jars are generated with maven). This would help dependency management if the jars are used in other projects.
4. Add a 'Automatic-Module-Name' entry to the manifest. This is helpful if the jars are used as dependencies in a Java 11 module-system project.
5. Add a 'Maven-Group' entry to the manifest.
6. Provide kotlin version from gradle.properties.
7. Provide java (release) version from gradle.properties
8. Provide dokka version from gradle.properties.
9. Updated gradle wrapper to 6.8.2
10. (Optional) removed .idea directory from git

Perhaps you find some points of this suggestions useful.

Kind regards,

aanno