accounts: pagination, server-side search

Pagination fully factored out, and both Activities and Accounts now use
a PaginatedList superclass. Server-side search is done by pressing enter
after typing a search, or by pressing the search button. Works on
accounts, soon will on activities if it doesn't already.

lang/admin/en-us.json

@@ -136,6 +136,7 @@
         "filters": "Filters",
         "clickToRemoveFilter": "Click to remove this filter.",
         "clearSearch": "Clear search",
+        "searchAllRecords": "Search all records (on server)",
         "actions": "Actions",
         "searchOptions": "Search Options",
         "matchText": "Match Text",
@@ -190,6 +191,7 @@
         "totalRecords": "{n} Total Records",
         "loadedRecords": "{n} Loaded",
         "shownRecords": "{n} Shown",
+        "selectedRecords": "{n} Selected",
         "backups": "Backups",
         "backupsDescription": "Backups of the database can be made, restored, or downloaded from here.",
         "backupsFormatNote": "Only backup files with the standard name format will be shown here. To use any other, upload the backup manually.",