remove firstValidPropertyDeclaration helper function

Item::propertyDeclaration(QString) does exactly the same.

Change-Id: I3a88e82110ea357c44fbd1f274087e993fec6ccc
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
turn JSSourceValue bools into flags

A byte saved is a byte earned.

Change-Id: I7155cb71dc63bafa403b92f6bfb671ab8d8303d2
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>