Clean up ProjectTree

Denoise namespaces, remove redudant QObject include access to static
instance in nonstatic method

Change-Id: Ic54cd0da90e72a981394996fccd74053a11352e0
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: hjk <hjk121@nokiamail.com>
NodesWatcher remove friendship to all Nodes

Since signals in Qt5 are public

Change-Id: I316105ba0d15efb5a041285f948a0843dd8322f8
Reviewed-by: hjk <hjk121@nokiamail.com>