Refactor HTTP clients, fix lyrics plugin

[carl-di-ortus]

Note - I'm rebasing this from #258. It might be easier to review that one first.

My original forked work can be seen here. I have opened a bunch of issues on my forked repository, with the things that bothers me most. I intend to solve them at a slow pace. I might create more PRs in the future, but as of now I don't see a point, as this seems unmaintained.

HTTP client

This PR removes 3 custom HTTP clients, with invisible dependencies (like wget), and replaces it with libxml-perl library calls. Simplified some callbacks. Now forcing all output as utf8.

Lyrics

It also contains a fix for parsing the updated musicmatch.com responses for lyrics plugin. A separate task should be opened to implement more providers or simplify the plugin file, also for bugs in current parser (there are some, like bad url when having '(' ',', ..., wrong h2 tag selected when result contains tags, ...).

Added new feature when response is detected to be instrumental, to write it nicely, in the style as default "No lyrics found" label.

Console output:

no lyrics found in /media/data/music/library/s/Shpongle/[2013-07-25] Museum Of Consciousness/03 - Shpongle - Juggling molecules.mp3
lyrics : loading https://www.musixmatch.com/lyrics/Shpongle/Juggling-molecules
found instrumental at /home/carl/source/gmusicbrowser/plugins/lyrics.pm line 460.

Removals

Removed Artist -> Events page, as the endpoint was no longer there.

Summary

This PR closes 3 tasks in my forked repo. It might solve #252, but I haven't tested, and I don't intent to test this. It might also help a little bit with #210, but I haven't check this out, also a relate bug issue is registered in forked repo here.