build: fix project pathmap with legacy repos

 some devices still use (display/media)-legacy. Enable those
 trees to be handled via project pathmap.

Change-Id: I38b75ea49b3f7f5736eaaf9370bb72b2aaa42320
build: Allow to remove packages via REMOVE_PRODUCT_PACKAGES.

REMOVE_PRODUCT_PACKAGES can be used by device configurations to
remove default packages. (ex. to reduce system.img size)

Change-Id: I2fdf74b642ae3f32905b70903e883dda9f67cc3a