Move out of alloc_algo code modifying the data model

This way the alloc_algo() becomes idempotent, simplifying implementation
of new alloc_algos as well as rolling abck if allocation fails (for
instance because some resource is exhausted at the time).

For now the code applying the results is moved to tbf::alloc_algo(), but
it will eventually get out of tbf code, so that the MS object is
responisble for running it. As a result, there's no even need to create
TBF object before trying to allocat resources, which will help furher in
rollback operations described above.

Change-Id: I5ffd00f5f80bde4b73b78db44896f65e70e12b20
---
M src/alloc_algo.cpp
M src/alloc_algo.h
M src/gprs_pcu.h
M src/tbf.cpp
M src/tbf.h
M src/tbf_dl.cpp
M src/tbf_dl.h
M src/tbf_ul.cpp
M src/tbf_ul.h
M tests/tbf/TbfTest.err
M tests/ulc/PdchUlcTest.cpp
11 files changed, 390 insertions(+), 375 deletions(-)