When a file is deleted, its cover no longer appears in grid view

[libreliodev]

This bug only occurs for non Newsstand apps

Steps to reproduce:

• if necessary, deactivate Newsstand in Application.plist
• download a magazine
• delete it in the downloads tab
• => the cover no longer appears on Grid

Proposed solution:

• in NSBundle+WAAdditions, create a method (int) countNumberOfReferencesForRessouceWithUrlString:(NSString*) urlString. This method should check all metadata files (ending with _metadata.plist) and count the number of times the resource is used
• in WALocalParser, in - (void) deleteDataAtRow:(int)rowat https://github.com/libreliodev/iOS/blob/master/Classes/WALocalParser.m#L212, do not delete resource if it is referenced in 2 or more metadata files

[quant-algo]

Fixed