Actually record timstamp on first iteration

Errors were reported about a lack of playlist updates for $time_since_epoch
before this fix.
Initial checks for cosistency of redundant streams

Doesn't work very well yet, as we report master-playlist inconsistencies
once a second, even though they do not update as often.  No deeper checks
currently implemented.
More HLS HTTP tests; should've comitted seperately

Including,
 - HttpExecutionWrapper to hook some common error handling code
   into several call-sites (especially the extra diagnostic on
   SocketTimeoutException, so we know what the remote address
   was in a multi-server environment)
 - Only require 'keep-alive' from the server for the very first
   request on a connection (to avoid problems reported just
   because the server closes the connection after some number
   of reuses)
 - Report the value of an X-Pkgr-Instance response header, if
   present, on unexpected HTTP responses
 - Report an HLS segments media-sequence-number when it appears
   in the context of a problem report
HLS segment PTS checks

 - Check that all initial PES packets in a segment have a PTS
 - Check that the initial PTS values for audio and video streams
   have the same value
Poll at 1* not 0.5*duration, and don't fall behind
Suppress complaints re. duration of past segments
Exponential backoff for m3u8-is-unchanged messages

So as not to spam the log
Fix spelling mistake
(Speculative) sanity check of any Age header
More diagnostics on ConnectionClosedException
Debugging an unexpected NPE
Remove disabled test code
Don't stop media manifest polling on error

Failures (predominantly timeouts) getting a manifest in one iteration were
preventing any further iterations from happening.
Comment to describe the point of a field
Detangle scheduling of media manifest refreshes
Allow process() to see/report on response headers
Inspect CODECS attribute of master m3u8 entries

Could eventually be the basis of checking media streams have the advertised
contents.
Fix string-format typo
Create a start-script for conformist
Use resonable duration even if initial load failed

NullPointerException will happen if first load of master m3u8 times out, for
instance.