PM-667 Updated the logic of constructing the path to the condor_dagman
on basis of environment profiles in the Site Catalog.

Updated Order of Preference for lookup is
1) Transformation Catalog
2) Site Catalog
3) Environment variables in the Environment
4) from system PATH
PM-667 the SubDAX generator now generates a prescript wrapper that
launches pegasus-plan from the correct directory. When the sub
workflows are planned we log at config level the various directories.
PM-667 the planner prescript wrapper needs to launch pegasus-plan from
local scratch directory. the directory created by the workflow for
local site.
Merge branch 'master' of https://github.com/pegasus-isi/pegasus