We were setting the -data parameter to the project root but this caused
the language server to fail initialization and synch of gradle
dependencies. As consequence ALE failed to work fully on gradle
projects.
This fix sets the workspace to the parent folder of the project root.
Normally this corresponds to the correct Eclipse workspace path.
When this is not the case, this fix also allows users to explicitly set
the absolute path to the workspace via configuration variable.
* Search eclipselsp jar and config files within system package path
* Allow setting an alternate eclipselsp configuration directory
* Add test for ale_java_eclipselsp_config_path
- Set default value to $HOME/eclipse.jdt.ls
- Make JAR search regexp more specific.
- Allow to set the VSCode extensions folder as ale_java_eclipselsp_path.
