configuration variables: where is the documentation?
In CiviCRM 4.6, but not in later versions, the source documents the following configuration variables:

$debug = 0;
$backtrace = 0;
$smartyDir = NULL;
$pluginsDir = NULL;
$templateDir = NULL;
$resourceBase = NULL;
$uploadDir = NULL;
$imageUploadDir = NULL;
$customFileUploadDir = NULL;
$imageUploadURL = NULL;
$extensionsDir;
$extensionsURL = NULL;
$cleanURL = FALSE;
$countryLimit = array('1228');
$defaultContactStateProvince;
$provinceLimit = array('1228');
$defaultContactCountry = '1228';
$defaultCurrency = 'USD';
$lcMessages = 'en_US';
$dateformatDatetime = '%B %E%f, %Y %l:%M %P';
$dateformatFull = '%B %E%f, %Y';
$dateformatPartial = '%B %Y';
$dateformatYear = '%Y';
$dateformatTime = '%l:%M %P';
$timeInputFormat = 1;
$dateInputFormat = 'mm/dd/yy';
$fiscalYearStart = array(
$moneyformat = '%c %a';
$moneyvalueformat = '%!i';
$currencySymbols = '';
$defaultCurrencySymbol = '$';
$monetaryDecimalPoint = '.';
$monetaryThousandSeparator = ',';
$gettextCodeset = 'utf-8';
$gettextDomain = 'civicrm';
$gettextResourceDir = './l10n/';
$userFramework = 'Drupal';
$userFrameworkVersion = 'Unknown';
$userFrameworkUsersTableName = 'users';
$userFrameworkClass = 'CRM_Utils_System_Drupal';
$userHookClass = 'CRM_Utils_Hook_Drupal';
$userPermissionClass = 'CRM_Core_Permission_Drupal';
$userPermissionTemp = NULL;
$userFrameworkURLVar = 'q';
$userFrameworkDSN = NULL;
$userFrameworkBaseURL = NULL;
$userFrameworkResourceURL = NULL;
$userFrameworkFrontend = FALSE;
$userFrameworkLogging = FALSE;
$maxImportFileSize = 1048576;
$maxFileSize = 2;
$localeCustomStrings = NULL;
$mapProvider = NULL;
$mapAPIKey = NULL;
$geoProvider = NULL;
$geoAPIKey = NULL;
$geocodeMethod = '';
$mapGeoCoding = 1;
$logging = FALSE;
$empoweredBy = TRUE;
$enableComponents = array(
$enableComponentIDs = array(1, 6, 2, 3, 4, 8);
$enableSSL = FALSE;
$fatalErrorTemplate = 'CRM/common/fatal.tpl';
$fatalErrorHandler = NULL;
$legacyEncoding = 'Windows-1252';
$fieldSeparator = ',';
$maxLocationBlocks = 2;
$captchaFontPath = '/usr/X11R6/lib/X11/fonts/';
$captchaFont = 'HelveticaBold.ttf';
$includeWildCardInName = 1;
$includeEmailInName = 1;
$includeNickNameInName = 0;
$smartGroupCacheTimeout = 5;
$defaultSearchProfileID = NULL;
$dashboardCacheTimeout = 1440;
$doNotResetCache = 0;
$includeAlphabeticalPager = 1;
$includeOrderByClause = 1;
$oldInputStyle = 1;
$formKeyDisable = FALSE;
$inCiviCRM = FALSE;
$componentRegistry = NULL;
$doNotAttachPDFReceipt = FALSE;
$wkhtmltopdfPath = FALSE;
$secondDegRelPermissions = FALSE;
$wpBasePage = NULL;


The 4.7 equivalent source is here