Allow system calls to pull global settings from the database.

This adjusts the System() class to first try local settings of the
supplied value, fall back to global settings, and then the supplied
default, before finally erroring. This corrects an issue where the
VideoGrabber() child class did not properly pull the global settings for
TelevisionGrabber and MovieGrabber, and thus just used the internal
defaults.
(cherry picked from commit 4e072b2de29c32c4d00fe62849feadd80d2c0c02)
Remove tmdb.py and associated library.
(cherry picked from commit 53c272dc4ffe2f5392ff54fb3e446801395274fb)
Remove tmdb library from python installer script.
(cherry picked from commit 9c0dfbc9f6b753a5b3d6f2e294baaf9577519a91)
Remove more tmdb bits.
(cherry picked from commit a5d54217962a706c4cedc33012e9e7049d4877f6)
Update Python bindings version.
MythMusic: fix playback of ogg radio streams

Peek the probe data from the stream buffer rather than read the data otherwise
ffmpeg fails to open the stream because the magic it is looking for has already
been read from the stream.

Also increase the probe buffer to 16K this seems to be required for some ogg
streams to be probed properly.

(cherry picked from commit 6b09d7c629e4efac81276eee9f4b7cbe3bc661ef)
Change RI::ForgetHistory() to use dupmethod when available.

Previously, ForgetHistory() implicily used subtitle and description as
the duplicate check method.  Consequently, it doesn't always match
correctly when other methods are used and there are guide changes in
data that should be ignored.  In addition, don't assume any dupmethod
in the Previously Recorded screen to avoid being to overzealous when
called from there.

(cherry picked from commit 567cba3184db0e5801dc1ae7736d5d778ec2d96c)
Fix startts copy & paste error in previous ForgetHistory() change.

Also, do use subtitle & description semantics when the original
information is no longer available, but do it in a way that can be
easily detected and works in all code paths.

(cherry picked from commit d2231e90b3f581c69e12cd376324a6b8cdf9ac65)
Clear duration and framecount flags with mythutil --clearseektable.

Otherwise those flags are hard to get rid of when mythcommflag
--rebuild doesn't produce a correct seektable for some reason.
(cherry picked from commit c4f0c0c57c87c4bfe2e9d143648df2a02c44d578)