Allow for multiple files per share

[ThatGuyJacobee]

Refactor some of the share logic to allow for multiple files to be shared per share. Would require expanding the table with another to resolve many-to-many relationship, plus refactoring the file shares area and file link access page.

[ThatGuyJacobee]

Should be easy for internal sharing, just a matter of creating extra records for each file selected.

For the external link sharing, an extra table will likely be needed as mentioned.