B2OC: try to cleanup line registration

A prototype here.

The basic idea is to avoid repeated copy/paste work when registering lines into hlt2/spruce_b2oc.py.

The new hlt2_b2oc.py file consists of four parts:

• import line_alg makers from separate files like b_to_dh.py, and store them in a python dictionary.
• book the lines with name of their decays in lists/dicts, separated into different purpose including
  • default lines, which is Turbo-like and no further configuration is needed.
  • prescaled lines, which is applied by a non-default (not 1) prescale value.
  • flavor tagging lines, which need some extra output for flavor tagging. (TBD)
  • isolation lines, which need some extra output for isolation variables. (TBD)
  • mva filtered lines, which a TMVA-based filter is applied.
• register the lines with looping the lists by generic functions.
• a few lines for special purpose can be registered in "old-school" at the very end of file.

To be discussed whether adopt this structure or not.

Problem

Registering lines with generic builders like

for decay in default_lines:
    @register_line_builder(hlt2_lines)
    def make_default_hlt2_line(name='Hlt2B2OC_%s_Line'%decay, prescale=1):
        line_alg = line_makers['make_%s'%decay](process=PROCESS)
        return HltLine(
            name=name,
            prescale=prescale,
            algs=prefilters.b2oc_prefilters() + [line_alg])

with same function name will bring trouble, the log looks like

...
LAZY_AND: moore                                                                                                #=286028  Sum=26          Eff=|(0.009090019 +- 0.00178262)%|
   LAZY_AND: Hlt2B2OC_BcToD0K_D0ToHHHH_Line                                                                    #=286028  Sum=26          Eff=|(0.009090019 +- 0.00178262)%|
   LAZY_AND: Hlt2B2OC_BcToD0K_D0ToHH_Line                                                                      #=286028  Sum=26          Eff=|(0.009090019 +- 0.00178262)%|
   LAZY_AND: Hlt2B2OC_BcToD0K_D0ToKsDDHH_Line                                                                  #=286028  Sum=26          Eff=|(0.009090019 +- 0.00178262)%|
   LAZY_AND: Hlt2B2OC_BcToD0K_D0ToKsLLHH_Line                                                                  #=286028  Sum=26          Eff=|(0.009090019 +- 0.00178262)%|
   LAZY_AND: Hlt2B2OC_BcToD0Pi_D0ToHHHH_Line                                                                   #=286028  Sum=26          Eff=|(0.009090019 +- 0.00178262)%|
...

All lines will be overridden by one line and produce same output. Don't know if it's possible to declare different function in the for loop.