Through configuration, the lte-softmodem can be halted to await a
reconfiguration from the lte-softmodem. A mutex and condition variable are used
to implement this.

Furthermore, the dependance of lte-softmodem.c on FlexRAN has been reduced to
one include and the flexran_agent_start() call.

- add set_function_spec_param() which configures RU_t instance depending on its
  function(al split)
- export more functions like kill_RU_proc() so that they can be reused by
  restart functionality

all the FlexRAN scheduling code is now also handled by the general OAI
scheduling code

- when changing values RC.rrc[i]->configuration should be changed too
- then, RRC_RECONFIGURATION_REQ will pass the changed conf down until PHY
- give warnings at functions that are not implemented

- rename functions
flexran_get_tdd_ack_nack_feedback() -> flexran_get_tdd_ack_nack_feedback_mode()
flexran_get_ue_pmi() -> flexran_get_ue_wpmi()

- defines RCconfig data structures
- adds method to read data
- use it in source files

Try to merge feature-68-enb-agent into develop
develop should be fast-forwarded later to this branch to complete the merge
This code does not compile yet. Among other things:
- the scheduler structure needs to be reworked for FlexRAN
- the config is structured differently. The files enb_config.{c,h} from develop
  have been copied in here, the files with merge annotations are in
  enb_config.{c,h}.before_merge
- the restart needs to be restructured, since the PHY vars data structure lives
  in RC now

- lock with mutexes
- don't start ENB_APP task, but Agent directly and wait in case of
  reconfiguration

- {restart,stop}_L1L2() in lte-softmodem.c
- add function start_phy_rrc() in enb_app.{c,h}, accessible from outside
- will be used to restart PHY and RRC when lte-softmodem is restarted

use only one FlexRAN wait function

- when exiting task, the task is set as "not configured"
- this permits to start a task again