README: reflect boost build change

link libcephfs-jni java parts instead of copying

README: document new build approach

update prebuilts

brief changelog:
ceph v17.2.3, openssl 1.1.1q, ndk r25.b

README: update status, drop WIP flag

while this is not done, it is already useful enough for general cases

update prebuilts

brief changelog:
ceph v17.2.1, with logcat hack, dirsize_rbytes=false performance fix
openssl 1.1.1p

jni: update to quincy

jni: update prebuilts from ceph v16.2.7 rebase, un-lfs

newer ndk r23.b toolchain seems to produce a lot smaller binaries, and
we can now get rid of lfs. old binraries are branched at
old-prebuilts-lfs branch on github.

update prebuilt ceph libs to pacific

initial commit