mapistore/oxio: Handle return values from Indxing.uri_for_fmid gfacefully
mapistore/oxio: move logger initialization in separate function

It is still a global logger - not very nice but will do the job
mapistore/python: Print out the error on Folder.open_message() failure
mapistore/oxio: Listing and open messages implementation
HACK: mapistore/python: preload libpython2.7 with RTLD_GLOBAL

This is for sesequent modules loading to work
HACK: Skip provisioning every time mailbox is opened
HACK: Makefile: don't install python backends - i'm using symbolic link
WIP: mapipstore_backend: Gather as much context as we can - don't fail if backend fail

oxio for instance doesn't support this call yet
HACK: oxio.py: Prefix folder names with 'OXIO-' so it is visble when it come from
Revert "HACK: Skip provisioning every time mailbox is opened"

This reverts commit c61f63c5c40fa3e964b281c1ad66635b92b8802f.