Make javaconfig.json optional and try to read other config files

Eclipse generates a .project for a java project. The presence of this file could also indicate the root of a Java project. Along with it, Eclipse generates a .classpath, which is an XML file like this:

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
    <classpathentry kind="src" path="src"/>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
    <classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/4"/>
    <classpathentry kind="output" path="bin"/>
</classpath>

It contains both the sourcePath setting (<classpathentry kind="src"/>), the outputDirectory (<classpathentry kind="output"/>) and the actual class paths (<classpathentry kind="con">). Eclipse does not have a feature to automatically export these into a text file this extension understands, support for this file would make it super easy to contribute to projects that use Eclipse.

Similarly, maybe we can take the presence of a pom.xml as the indication of a java project root aswell and get classpaths for Maven projects directly from the extension without someone having to add this configuration to their pom.xml?

Would do a PR 😃

[georgewfraser]

pom.xml is now read automatically: https://github.com/georgewfraser/vscode-javac/commit/ea0a36887374ee22e06a2009a602bcd5a479591a

@felixfbecker @xastor reading eclipse .project would be similar, PR welcome

[georgewfraser]

I would suggest starting simple: a separate source file. If we make some good progress, it can be spun off as a separate module later.