Preview edit file (#2369)

* Revert "update share link permission (#2328)"

This reverts commit 6313e54dd7.

* update share link related UI

Download link(s) to Share link(s)

* update file api

add 'can_preview' and 'can_edit' fields

* update view file page

'invalid extension' to 'File preview unsupported'

* update share popup

1. send file detail request to check if can preview/edit file
2. show or hide share link permission according to api response
3. add tests for can_preview/edit_file func

* use FILEEXT_TYPE_MAP to check if can preview file

static/scripts/app/views/dirent.js

@@ -372,11 +372,9 @@ define([
             this.hideMobileMenu();
             var dir = this.dir,
                 obj_name = this.model.get('obj_name'),
-                can_preview = this.model.get('can_preview'),
                 dirent_path = Common.pathJoin([dir.path, obj_name]);
 
             var options = {
-                'can_preview': can_preview,
                 'is_repo_owner': dir.is_repo_owner,
                 'is_virtual': dir.is_virtual,
                 'user_perm': this.model.get('perm'),