Initial implementation of NetworkScoreManager's backing service.

This service will ultimately be responsible for propagating scores
down to lower-level network subsystems. For now, it just keeps scores
in memory and exposes these for debugging purposes via "adb shell
dumpsys network_score".

This change also adds provisioning of a default scorer. When
NetworkScoreService is first initialized, it checks to see if it has
ever set a default scorer; if not, it reads a package name from a
build config property and attempts to set it as the default.

Also add autogenerated equals/hashCode methods to all parcelables.

Bug: 14111427
Bug: 13786258
Change-Id: I02271171653d42e12acd240b73b9e23950744f6b