manifest: android-8.0.0_r30 -> android-8.1.0_r1 & lineage-15.0 -> lineage-15.1

Also switch to AOSP's versions of the following repos
 - external/libnetfilter_conntrack
 - external/libnfnetlink
 - system/hardware/interfaces
 - system/netd

Change-Id: I46fb1ef95cef62cc7f5f1600c3e578660f034e12
3 files changed
tree: 792ef1f619817047fb47cbf9c238e6ffe2a1817a
  1. snippets/
  2. default.xml
  3. README.mkdn