Initial revision of gmt BedToIntervalList wrapper for Picard tool.

Initial revision of gmt BedToIntervalList wrapper for Picard tool.

The hard-coded path to picard 1.123 should be removed once @iferguson90 changes are made to G:M:T::Picard related to package name changes for version 1.123
I think it can cause some subtle problems when we explicitly call exit in tests - can't remember what it is though.