Move apksig library from build/tools/apksigner/core.

This moves build/tools/apksigner/core to its own project tools/apksig.
The move also renames the moved Java packages from
com.android.apksigner.core.* to com.android.apksig.* to reflect the
new name of the library.

Bug: 27461702
Change-Id: I44079ddba47b7897a9ad6c0b1aaf4540e6fd284c
35 files changed
tree: b713bd57567deb750d1225df17b4b169cd8d20ab
  1. src/
  2. Android.mk