Syntax errors fixed, naming convention applied, wrappers used:

Syntax errors fixed, naming convention applied, wrappers used:
- Some syntax errors fixed (were added with last commit)
- Naming convention applied on variables $max ($numMenus) and some more
- Wraper countSumTotalData() further used
- overview-inc.php contained a query which can be converted into a wrapper call,
  function isExtensionInstalled() could be used instead
- TODOs.txt updated