OBSELETE: Add doubly charmed baryon lines

This MR is superseded by !1508 (merged). This MR will be deleted once !1508 (merged) is merged.

Add doubly charmed baryon lines based on the Run2 implementations, including the Xicc++, Xicc+ and Omegac+ decays to charmed baryons and charmed mesons.

The code is organized into two files:

• lines/xicc/stage.py which contains particle filters and combiners which can be commonly used.
• lines/xicc/Xicc.py which contains the definitions of doubly charmed baryon lines.

The algorithms.py is modified to include N5BodyCombiner and N5BodyCombinerWithPVs, which are used to combine multi-body decays.

As a first step, the Hlt2XiccpToLcpKmPip_LcpToPpKmPipLine of the Xi_cc+ -> Lambda_c+ K- pi+ decay and the Hlt2XiccppToLcpKmPipPip_LcpToPpKmPipLine of the Xi_cc++ -> Lambda_c+ K- pi+ pi+ decay are defined and tested. The charts of control flow control_flow.pdf and data flow data_flow.pdf are attached. For the test with Minbias Upgrade MC of 1000 events, no candidates are reconstructed, which is as expected. For the test with XiccpToLcpKmPip Upgrade MC of 1000 events, we get

LAZY_AND: Hlt2XiccpToLcpKmPip_LcpToPpKmPipLine                    #=1000    Sum=106         Eff=|( 10.60000 +- 0.973468)%|

For the test with XiccppToLcpKmPipPip Upgrade MC of 1000 events, we get

LAZY_AND: Hlt2XiccppToLcpKmPipPip_LcpToPpKmPipLine                #=1000    Sum=19          Eff=|( 1.900000 +- 0.431729)%|

A total number of about 40 lines are defined in the same manner, including Lcp, Xicp, Xicz, Dz, Dpm, Ds as intermediate states.

The TODO list includes:

* The Hlt1 TISTOS filter
* Monitor histograms
* ReFitPVs configuration

Further studies include:

* The detailed selection requirements are to be tuned with Upgrade MC.
* The selective persistence is also to be explored.