use current playing file title as alternate name

=description of the change=

issue:
seeing as a lot of times it happened to me where taiga didn't recognize an anime file i was playing because its title was different from what it was expecting(Japanese vs English vs random translation mix the fansub group decided to use) i found myself adding alternate titles all of the time.
unfortunately with the current flow it was somewhat cumbersome, as i needed to copy the name manually(and be careful with what part of the filename i'm copying).

solution:
so to make this easier i decided to implement a button to do all of that automatically for me.
1. i started by implementing it in the animelist page because there existed the "edit" context menu which already had an option to edit the alternate titles, so logically it was the most straightforward to add it there.
2. then i also added it in the info page for the anime, though i don't anticipate much use of that button.
3. and i also added it to the search results page, so when i'm playing an anime i have yet to add to my list i wont need to first search, then add then go to the anime list view and add an alternate title, but instead finish everything from the search panel.

possible addition:
i was thinking about adding an "add to currently watching and use current file as alternate title" button to make the process faster, but maybe later.


=forking, pull requests & cpp = 
i should note that my experience with cpp is fairly limited as most of my programming is done in c#, 
i tried to maintain reasonable practices and not mess around with your code too much. 
but if i did anything wrong i would be happy to fix it so just LMK

moreover this is my first attempt at forking& making a pull request, so i am not sure what are the best practices for that in terms of commit msgs etc.

i could merge everything into a single commit,
or i could make each of the changes into a different pull request if you want to pick and choose.