Add feature to view admin_audit log files

Add a LogFileProvider class that identifies the available log files
It checks if the admin_audit app is enabled, and fetches it's logfile
path.

Additionally, add ability for user to select the file they want to
view. The "Download logs" button now downloads the currently selected
log file.

Tested by enabling/disabling admin_audit app, toggling "Log file"

Signed-off-by: Lakshaya Tohan <lakshaya.tohan@gmail.com>

appinfo/routes.php

@@ -14,9 +14,11 @@
 	['name' => 'log#get', 'url' => '/get', 'verb' => 'GET'],
 	['name' => 'log#poll', 'url' => '/poll', 'verb' => 'GET'],
 	['name' => 'log#search', 'url' => '/search', 'verb' => 'GET'],
+	['name' => 'log#download', 'url' => '/download', 'verb' => 'GET'],
 	['name' => 'log#getSettings', 'url' => '/settings', 'verb' => 'GET'],
 	['name' => 'log#getLevels', 'url' => '/levels', 'verb' => 'GET'],
 	['name' => 'log#setLevels', 'url' => '/levels', 'verb' => 'PUT'],
 	['name' => 'log#setRelative', 'url' => '/relative', 'verb' => 'PUT'],
 	['name' => 'log#setLive', 'url' => '/live', 'verb' => 'PUT'],
+	['name' => 'log#setLogFile', 'url' => '/logFile', 'verb' => 'PUT']
 ]];