[javaimport.el] Finalized class provider looking for all classes in all JARs located in the current folder.

I may need to filter more the classes detected, as for example inner-classes used for Groovy closures may be wrongly detected
as classes that can be imported in source code (something looking like package.MyClass$InnerClass$1_closure$11_closure2).

There is now 2 providers: one looking for classes directly defined in Java or Groovy source files (.java/.groovy files),
and one scanning JAR file contents for all compiled classes inside (.class file).

TODO: make a provider returning classess stored in some kind of cache files, being just text files with a custom list of class
we want to be proposed as candidated when searching for imports (it will be typically used for storing classes from JDK or Groovy SDK,
but it can be used to add any list of classes we want provided by the tool).
Merge branch 'master' of github.com:laurentpsychedelic/settings