Implements album art auto retrieval with caching

See merge request brian/mymusiclist!12

Add unique email constraint for User

See merge request brian/mymusiclist!11

> Changes Ed Sheeran's album named multiply from × to x, which fixed album art finding
  for this title.

> to use, download 'pip' which is python's package manager, then run pip install musicbrainzngs.
> tested using python2.7

Refactor the whole codebase

See merge request brian/mymusiclist!10

Adds search features, album views, artists views, and increases dummy data size

See merge request brian/mymusiclist!9

Merge branch 'playlistwip' of ssh://gitlab.discs.ateneo.edu:15316/brian/mymusiclist into playlistwip

Searchnav

See merge request brian/mymusiclist!8

Merge branch 'playlistwip' of ssh://gitlab.discs.ateneo.edu:15316/brian/mymusiclist into playlistwip

Minor design changes for Home Page

Added a search.html, can select search by <type>, connected search results to album/artist profile, removed unneccesary search+<text>.html

> /artist/<id>
> /album/<id>

Added a search bar in base.html, and 3 different searches. Only album search is working with the search bar as of now.