[Jar installer] Fixed building of dependency graph tree.

Hi,

This is another issue in the Fabric master that prevents users from installing jar as a managed process. 

`JarInstaller` tries to resolve dependency tree against installed jar's POM, but `File` instance you pass to the resolving method (`mavenResolver#collectDependencies`) represents jar file, not POM file. That results in an attempt to parse JAR input stream with XML parser and error returned to the Karaf shell.

I changed to method used to resolve dependency tree to one taking jar as a parameter (`mavenResolver#collectDependenciesForJar` instead of `mavenResolver#collectDependencies`). After this change the dependency graph tree is properly resolved. Also added appropriate unit test.

Cheers.