Add grace-period to bypass the local tvdb show status 'ended' check.

The bypass introduces a sliding window of +/- 30 days from the
latest aired EP airdate and -30 day before next unaired EP airdate
where we will get the latest data from tvdb.
We exclude season 0 at this time from this check to prevent abuse.
This should prevent the need to do 'force full update' to fix shows
that get their status changed incorrectly while still reducing the
hits to tvdb for shows that are in-fact ended.

Added 'ended' bypass on to prevent older shows with no next aired ep
from being missed (ex Arrested Development or shows that have a
solid year or more between seasons - like Sherlock)
Add last_update_tvdb for controlling nigthly showupdates

+ move setTVRID into own try for correct error log message
Upgraded tablesorter 2.1.19 -> 2.13.3
Merge pull request #769 from thezoggy/dev--update_tablesorter

Upgraded tablesorter 2.1.19 -> 2.13.3
Change start options + added help text

+ create pid decision outside loop,
  otherwise using: --pidfile= --daemon is not creating pidfile
+ location pidfile in error output (debugging scripts)
+ rewrite some messages
+ unify exiting with sys.exit
Merge branch 'add_should_update_ended_shows_dev' into development