Revert "CMakeLists: Re-enable building of examples & all library features"

This reverts commit 4767c92b106e9ac7758c3d2c707729c1d0718ebe.
JsonSerializer: Break up serialization & unserialization methods

* The behind-the-scenes serialization/unserialization implementation
is now encapsulated by two new methods: write & read (respectively).
This means that the serialize & unserialize methods are now filestream
interfaces.

* The stringify method now outputs a JSON string of the input
nom::Value as expected.
ptree/Value: Fix copy assignment operator

* Each value type should now be properly copied over when using the
equality operator.
ptree/VString: Bit of clean up

* Introduce ArrayIndex typedef
* Comment out operator[] implementation; these are never used.
examples/values: Introduce yet another unit test