Prevent JDTLS from generating metadata files at project root (#179)

Address #178 

Add -Djava.import.generatesMetadataFilesAtProjectRoot=false system
property to stop .project, .classpath, and .settings/ files from being
created in the project directory.

Author: tartarughina

src/jdtls.rs

@@ -77,6 +77,7 @@ pub fn build_jdtls_launch_args(
         ),
         "-Dosgi.sharedConfiguration.area.readOnly=true".to_string(),
         "-Dosgi.configuration.cascaded=true".to_string(),
+        "-Djava.import.generatesMetadataFilesAtProjectRoot=false".to_string(),
         "-Xms1G".to_string(),
         "--add-modules=ALL-SYSTEM".to_string(),
         "--add-opens".to_string(),