Add **kwargs to LibrarySection.get() for arbitrary query parameters.

[lidocaineus]

Whenever there are title collisions when calling LibrarySection.get(), the first matching element from the query is returned. This patch adds arbitrary key / value pairs to .get() to support optional parameters beyond just "title", enabling more complex searches by adding the additional search parameters to the key; this (hopefully) should enable the correct element to be returned. This is supported already in the Plex XML API but doesn't look to be implemented here. This shouldn't break any existing queries.

Example using "The Killers" originally from 1946 and remade in 1964; the query without additional parameters returns the first element which in this case is the 1946 version:

>>> plex.library.section('Films').get('The Killers')
<Movie:1563:The-Killers>

>>> plex.library.section('Films').get('The Killers', year="1964")
<Movie:1562:The-Killers>

>>> plex.library.section('Films').get('The Killers', year="1946")                                                                     
<Movie:1563:The-Killers>

Other parameters beyond year:

>>> plex.library.section('Films').get('The Killers', guid="com.plexapp.agents.imdb://tt0038669?lang=en")                                                                                                                                                                     
<Movie:1563:The-Killers>

Combinations:

>>> plex.library.section('Films').get('The Killers', year="1946", guid="com.plexapp.agents.imdb://tt0038669?lang=en")                                                                                                                                                                     
<Movie:1563:The-Killers>

[coveralls]

Coverage decreased (-5.6%) to 65.375% when pulling 84c84e5 on lidocaineus:LibrarySection.get_kwargs into fe27d76 on pkkid:master.

[Hellowlol]

Thanks for the PR. If .get can return more then one object you should use search that already supports what this pr implements.

[Hellowlol]

Closing this as i dont think it adds any real benefit. You can use .all(year=1111) or search to do the same thing. Maybe was should add logging if we have more then one item so the user knows it.

[lidocaineus]

Using search works so that's fine. That said it really should be emphasized that .get() is basically "best effort" and somewhat useless, as any sanity checking on what's returned would better be done using .all() instead.

In other words the function works, but it's usability outside a narrow use case is zero, not to mention it arbitrarily restricts the underlying XML request to "title" (this could've been any of a number of things but someone hardcoded it) instead of exposing its full functionality; my suggestion is it be deprecated and eventually removed.