Add multi-input support to drmemtrace analysis framework

While the drmemtrace scheduler supports multiple input workloads each with their own thread inputs, the analyzer framework and launcher do not make this easy as they take just one directory of input files all of which are treated as one workload.

Action items are:
+ Add launcher option to take multiple directories
+ Add launcher options to set core limits and priorities separately for each input directory
+ Add inter-process vs intra-process switch stats to schedule_stats
+ Add letter-per-workload instead of letter-per-tid to schedule_stats string schedule output