get_exit_code in the shell adaptor now returns None if no exit code is available (instead of raising an exception)

This closes #350
remove an error check which screwed with proper error reporting
use "file://" as default schema
add some default settings
add some default settings
implement file connection cache

this needs the new release manager in radical.utils, devel branch
move a method around
increase PBS job state delay; more shell leasing
fix typo, guard against threashing on pbs monitor errors
merge
Merge branch 'devel' of github.com:radical-cybertools/saga-python into devel
snapshot
fix bookkeeping in pbs adaptor, to avoid double accounting after get_job()
make sure lease manager exists once per session
get rid of deepcopy wherever possible
remove superflous sleep
fix reconnection problem
fix typos
Incremental fix for qstat on pbs pro.
Include "historic" jobs and add Finished state for PBS Pro.
disable some debug logs