medialib folder import should be more flexible

Before posting

Please follow the steps below and check the boxes with [x] once you did the step.

[x ] I checked the issue tracker for similar issues
[o] I checked the changelog if the issue is already resolved
[o] I tried the latest Clementine build from here --> no but Archlinux is almost current...

System information

Please provide information about your system and the version of Clementine used.

Operating System: Archlinux
Clementine version: Name : clementine Version : 1.3.1-9 Beschreibung : A modern music player and library organizer Architektur : x86_64 URL : http://www.clementine-player.org/ Lizenzen : GPL Gruppen : Nichts Stellt bereit : Nichts Hängt ab von : chromaprint crypto++ fftw gcc-libs glew glib2 glibc gst-plugins-base-libs gstreamer libcdio libechonest libgl libgpod liblastfm libmtp libpulse libx11 protobuf qjson qt4 sqlite taglib zlib Optionale Abhängigkeiten : gst-plugins-base: "Base" plugin libraries [Installiert] gst-plugins-good: "Good" plugin libraries [Installiert] gst-plugins-bad: "Bad" plugin libraries [Installiert] gst-plugins-ugly: "Ugly" plugin libraries [Installiert] gst-libav: Libav plugin [Installiert] gvfs: Various devices support [Installiert] Benötigt von : Nichts Optional für : Nichts In Konflikt mit : Nichts Ersetzt : Nichts Installationsgröße : 20,73 MiB Packer : Felix Yan felixonmars@archlinux.org Erstellt am : 2017-08-03T23:30:17 CEST Installiert am : 2017-08-10T01:09:21 CEST Installationsgrund : Ausdrücklich installiert Installations-Skript : Nein Verifiziert durch : Signatur

Expected behaviour / actual behaviour

Problem: all my audio media is a huge 300GB backup of my CD colledtion. each CD is backed up in flac, org and mp3 - so each song exists at least 3 times somtimes older backups exist in folders like archive or old

so when importing the lib to clementine I only want to add e.g. all ogg's but exclude everything in archive or old folders. Also most modern backups include a m3u file - so if a folder contains a m3u file this should be parsed, otherwise the files should be added by name

summary: when adding a folder as medialib

files should be filtered by mask - at least by extension
folders should be exculded by name / mask
interpret m3u files if existent

Steps to reproduce the problem (only for bugs)

currently if i add my collection folder als lib and select a song, this song almost always is played 3 times in a row as it exist in 3 different versions in the tree

clementine-player / Clementine