~xdavidwu/saf-cephfs

DocumentsProvider: don't hardcode log tag everywhere
ProxyFileDescriptorCallback: handle IOException
DocumentsProvider: set up ceph on create
DocumentsProvider: deduplicate ceph operation error handling
DocumentsProvider: handle mount IOException
CephMount: add missing IOException throw to mount()
add option to bypass file permission
build: update toolchain
support create
add write flag if writable
handle IOException from jni
root: expose more info
improve error handling
reuse mount
impl openDocument
initial commit