Removed UTF-8 forced encoding in variable varule escaping, and replaced htmlentities with htmlspecialchars.

- Multiline bracket notation is no longer allowed for expressions because of
  JavaScript/CSS clashes.
- Variables in expressions can now be preceded by characters unequal to `$',
  which will be prefixed to the variable evaluation.

- The Template class represents a template file, consisting of blocks and
  variables.
- The Node class is used to create a tree structure of the blocks in a
  template file, and of the data that is mapped on the blocks.

- Base file, contains some common classes and functions for use in the
  framework.
- An autoloader class, to load PHP classes in a specific directory.
- A logger class with functionality similar to the Python built-in `logging'
  module.
- Unit tests for the files listed above.
- README and git/unit tests/documentation config files.