Added Python module names index (PY-6923)

The index contains a map from module name (without '.py') to its
VirtualFile. The index stores '__init__.py' files under their package
name.
Added Python modules to 'Navigate to class' and 'Navigate to symbol' results (PY-6923)
Changed the visual representation of PyFileImpl to be more Python module-like (PY-6923)

For modules only names are shown (no extensions). For '__init__.py'
files representing packages only package names are shown (its parent
directories).
Merge branch 'goto-module'
CPP build
IDEA-119691 Groovy: References to outer class properties should be resolved to accessors if they exist. Fields are prefferable only inside its containing class (not inside inner classes of the outer class)
IDEA-117643 don't add parameters for binding variables. Just try to infer them as they are.
duplicated code
IDEA-117643 use a correct file for searching for binding variables. Complete binding variables in debugger's watch editor
unused field
don't load modules from disabled plugins
new inference: avoid current type calculation during conflict resolution for target type detection (IDEA-121052)
new inference: ensure type parameters are not modified during ground type evaluation