[incremental] Manager, Storage and changes to Package Manager Service

Checking in basic high-level classes and their interactions with
package manager service.

Incremental Manager manages IncrementalStorage instances. Both are
backed by Incremental Service.

Package Manager Service uses Incremental Manager to handle file
operaions on Incremental File System, such as renaming and cleanup.

Also adding place holders for native library handling.

Test: builds
Change-Id: I78b64f795de480e109aeaffe61272a413a6b4be5