Add particle flow ART tests and update tier0 particle flow configuration to fix a bug.

Adds a new package, PFlowTests, which runs some ART tests of reco from ESD for particle flow related reco setups. Two new job option files are also added inside eflowRec to be used by these tests. Usage of tau-PFO/FE links is enabled by default with this change (it was a bug that it was disabled by default) - this only changes the tier0 output by adding missing data (note that anyway AMI tags were enabling this by postExec up until now). No existing data is changed. Flagging AOD output change to SPOT (@amete) - you should see increases for taus and PFO/FE due to this (unless your tests had the postExec to enable it), but it ought to be small (and soon we would remove the PFO containers once we finalise validation of the FE, leading to an overall drop in size of particle flow AOD content). The flags are slightly reorganised such that all flow element link algorithms go under the control of one python flag.