Gittrac #4171:  Split a bunch of lines with continuation characters
to make sure that works properly.
Gittrac #4171:  Fixed the basic problem, but lots of cleanup needed
(including other places that use the "read a whole file into a string"
functionality).
Gittrac #3843:  We no longer look at HTCondor submit files if we're in
default/workflow log mode; also, we no longer distinguish between
using the default log for a node because we're in workflow log mode
overall vs. using the default log because there's no log file specified
in the submit file -- that simplifies a bunch of the code.
Gittrac #4171:  Cleaned up and documented the MultiLogFiles::FileReader
class.
Changed things around so that we only generate the event mask
string once, since it's the same every time.
Gittrac #4171:  Should be pretty much finished up -- DAGMan no longer
uses any of the "read a whole file into a string" methods, except for
finding the log file for a Stork submit file; removed a bunch of
MultiLogFile methods that used or implemented the "read a whole file
into a string" functionality.  (Still needs version history entry.)
Gittrac #4171/gittrac #3843:  Added version history items for these
bug fixes.
Merge branch 'V8_0-gittrac_4171-branch' into V8_1-gittrac_4189-branch
Gittrac #4189:  Initial merge is complete, but needs further checking
and maybe extension of the DAGMAN_USE_OLD_DAG_READER configuration
macro.  Also, the job_dagman_dont_use_default_node_log test fails for
a reason I haven't figured out yet.