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