New HLT2 lines for D0->h0l+l- and D0->h0pi+pi-

This MR adds HLT2 lines for:

• rare three-body decays D0->h0ll, where h0=KS0(LL,DD) and ll=ee,mumu,mue
• hadronic control modes D0->h0pipi

Files touched:

• rare_charm_makers.py: definition of new D0 maker for D0->h0ll decays
• d0_to_h0ll.py: 14 new lines added

Estimated Bandwidth:

• Total (14 lines): 0.5 MB/s (see table below)