Add thread pool in MangaCrawler that improves performance for get the chapters
Add date and title to thumbnail and limit at 5 the number of last chapters downloaded
Add chapter number to thumbnails
Add empty thumbs as indicator of execution tasks and a spinner when images are loading
Merge branch 'master' of https://github.com/Vrael/eManga

Conflicts:
	src/main/java/com/emanga/services/MangaCrawler.java