Use bulk mode in class name completion (fixes #40)

[derSascha]

Running Java class name completion on large jar files (e.g. Spark, 35MB, 22K Classes) takes long (e.g. Class names with an A takes ~180 Seconds).

Open the jar and seeking to the class on each class takes very long: https://github.com/bobbylight/RSTALanguageSupport/blob/c4ff0a2d6cc12e0b7f39e814c9a1dee2db5b5dca/src/main/java/org/fife/rsta/ac/java/buildpath/JarLibraryInfo.java#L96-L104

Instead of open the jar on every class, use the bulk API on class name completion. This reduce the time in the example above to ~3s.

[derSascha]

@bobbylight what do you think about the PR? Its a very small but very power full fix.