* Cleanups and reduction of copying
* Add STArray::back, operator[], push_back(&&)
* Add make_stvar
* Rework STParsedJSON
* Fix code and unit tests that use STParsedJSON
* STTx move constructor
* This silences a warning about a redundant cv-qualifier.
* This makes future coding mistakes about redundant
cv-qualifiers much less likely.
* This makes the code easier to read.
This introduces the STVar container, capable of holding any STBase-derived
class and implementing a "small string" optimization. STObject is changed
to store std::vector<STVar> instead of boost::ptr_vector<STBase>. This
eliminates a significant number of needless dynamic memory allocations and
deallocations during transaction processing when ledger entries are
deserialized. It comes at the expense of larger overall storage requirements
for STObject.
