run_server: Added more logs

Also run_server writes logs to $path/run_server.log in addition to
stderr.
Prepended timestamp for every log's line.
client: Added is_final field to result_entry

It checks for DNET_FLAGS_MORE and returns true if it is a last packet in
transaction.
client: Added new filters for entry::is_final

They are: positive_final, negative_final and all_final, so this filters
pass only final packages in every transaction. It may be usefull for
testing purpuses.
client: Fixed time formatting in file_logger
pytests: Fixed test for existen filters
linking: Fixed linking errors at Fedora 20
client: Fixed bulk operations

Added missed acquering of backend_id of target host for id in
dnet_state_search in case if it's not the first state in group's hash
ring
linking: Fixed one more linkage error at Fedora 20
indexes: Fixed set_indexes in multibackend systems

There was an error when shard of indexes' list of key for this key is
stored at the machine but different backend as list of indexes for this
key. We have to send UPDATE_INTERNAL commands to other backend but
otherwise it was processed on the same one.

For fixing this issue there was implemented a mechanism which makes
possible to asynchronously send commands to other backends at the same
node and receive replies back to this backend's io pool.
pytests: Fixed test_indexes_dict test

We need to check count of only final positive replies to ensure that
command was executed succesfully.