[WIP] PHP5.3+, PSR-4, Namespaces

This is a **Work-in-progress** branch.

*WARNING: Not suitable for usage, broken. Will be rebased, force-pushed, etc.*

- [x] Convert library-classes to use namespaces
- [x] Use PSR-4 autoloader
- [x] Remove php52 fence-files around JsonLD Parser/Serialiser
- [ ] Convert tests to use new namespace-based names of library classes
- [ ] Make sure that tests do not fail