This commit contains work done by Eurecom and by Benetel.

Final --phy_simulators warning removals for this branch, and former polar coding function corrections

--phy_simulators warning removals, except for nr_dlsim. Polar coding old implementation's approximation and a priori information options needs to be corrected or removed

added optimized polar decoding to UE DCI processing. Still to be tested. Changed decoder API to return XOR(CRC,rxCRC) which can be used to check for RNTI at receiver. For PBCH it returns 0 on positive CRC, !=0 on CRC mismatch.