Fix icon for manifest import and mention manifest feature in API

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/views/projects/_import_project_pane.html.haml

@@ -45,7 +45,7 @@
       %div
         - if manifest_import_enabled?
           %button.btn{ type: "button" }
-            = icon('file', text: 'Manifest file')
+            = icon('file-text-o', text: 'Manifest file')
 
   .js-toggle-content.toggle-import-form{ class: ('hide' if active_tab != 'import') }
     = form_for @project, html: { class: 'new_project' } do |f|

lib/api/settings.rb

@@ -25,7 +25,7 @@ module API
       optional :default_snippet_visibility, type: String, values: Gitlab::VisibilityLevel.string_values, desc: 'The default snippet visibility'
       optional :default_group_visibility, type: String, values: Gitlab::VisibilityLevel.string_values, desc: 'The default group visibility'
       optional :restricted_visibility_levels, type: Array[String], desc: 'Selected levels cannot be used by non-admin users for groups, projects or snippets. If the public level is restricted, user profiles are only visible to logged in users.'
-      optional :import_sources, type: Array[String], values: %w[github bitbucket gitlab google_code fogbugz git gitlab_project],
+      optional :import_sources, type: Array[String], values: %w[github bitbucket gitlab google_code fogbugz git gitlab_project manifest],
                                 desc: 'Enabled sources for code import during project creation. OmniAuth must be configured for GitHub, Bitbucket, and GitLab.com'
       optional :disabled_oauth_sign_in_sources, type: Array[String], desc: 'Disable certain OAuth sign-in sources'
       optional :enabled_git_access_protocol, type: String, values: %w[ssh http nil], desc: 'Allow only the selected protocols to be used for Git access.'