Prevent sc_update from being changed by an incoming slice reconfiguration
change while writing data to the scheduler

- flexran_agent_ue_config_reply() and flexran_agent_ue_state_change() send
  slice_id

Incoming slice configuration changes are buffered in an intermediate structure.
The MAC scheduler periodically polls the agent about changes. If there has been
a slice configuration change, apply it.

adds support for:
* create/remove slices
* change UE-slice association
* read/write slice parameters
* find slice index via ID

slice_counter had a wrong condition, not scheduling in DLSCH if the number of
slices is greater than one

- introduce structure in RC for slicing conf (UL/DL)
- move global variables regarding slice configuration into RC
- change ue_slice_membership(): consider UL/DL
- remove the unnecessary header files
- set default parameters: one slice

Summary of changes:
- some work on better parallel processing of eNB
  try the eNB with options: --fepw --codingw
- small changes for multi-UE simulation and simulation accuracy
  (UE power levels)
- initial work for the UE to use TUN device instead of ue_ip.ko
  only done for oaisim, default bearer, compile with:
    ./build_oai --ue-nas-use-tun <rest of options>