Removing files, more optimalizations and closing on first release

• Library now checks for missing files in selected paths and if library contains a file that is not present, it removes it from library.
• Maintenance thread was significantly slowed down to work every 10s, but on the other hand can be now invoked while waiting - this is used by inotify for immediate file detection and import.
• Imports are not disabling the album view until the model is being filled - if you are importing more files, you can play already imported files while new ones are being imported. (this also fixes the scroll back to top of the icon view on every refresh/import)

Inotify is here! Also multiple library paths

This is a huge update (again, I should really stop with these 600 additions commits, but I digress).

Main feature is the import GUI/Dialog, which is now available. It allows you to start/stop the import (button on address bar stayed, but has refresh icon instead) and most importantly add multiple folders and remove folders from which library should be imported.

The basics of Inotify were also implemented. There is a minor flaw tho. When something is modifying a watched folder (not a user just copying files) - if there is file creation and folder creation immediately after the file was created, the event for folder creation won't be fired. This results in the new folder not being watched, and manual refresh is needed.

Also, search is now enabled again.

v0.3-pre

This release contains big rework of original GUI workings and library import. The rework is not finished yet, but it shouldn't take much more time. This is preparation of code base for more new features.

First time experience is now much more polished. Import does not start automatically, which gives you option to select your address first. For now, you can have only one address at the same time. You can import files from more than one address, by importing each individual address you want. The library won't delete already imported files when changing path. Keep in mind, library won't keep track of any file changes yet - except manually importing new files.

This update temporarily disables search function. It was not reliable anyway and is not compatible with new reworked code. It will probably be reworked for next release.

v0.2-pre

This is the first actually use-viable version. Once the library is imported, it does not reimport on next start (neither does it check for new nor changed files tho).
Double-clicking album now loads the actual album instead of a folder where the first file is located.
Text is now properly centered and shows artist under album name (formerly shown in a tooltip).
Cover art is now saved into the same file as other library data to speed up startup.

First release!

This is a very early development build, not ready for production use.