437493 ProjectRegistryRefreshJob double refresh during projects import and classpath container initialization

Fixes #20

Signed-off-by: wecai <wecai@ebay.com>
431080 added test for flat directory layout

Fixes #21

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=431080
Signed-off-by: Anthony W. Juckel <ajuckel@gmail.com>