Get account data improvement

[Cylix]

Small improvement of getAccountData.

• Remove the returnAll parameter which is kind of pointless for that function
• Reuse the return of getNewAddresses for transfers & balances (avoid regenerating the same addresses over and over again).

The improvement results in twice as fast on testing data (as demonstrated by the screenshot below).
The improvement should be more significant for accounts with a large number of addresses.

Before:

After:

[Cylix]

I also addressed #194, but turns out it does not improve much (tried different seeds).
I case the case covered by the improvement does not happen frequently enough.

[Cylix]

Please do not merge immediately, still doing some experiments.

[Cylix]

Just addressed #194 optimization comment. It now goes as fast as Java library and can go a little bit faster by doubling the number of threads in the parallel_for.

Before merging this issue, I will check some places where we can initialize the hash in Models::Bundle (I added Models::Bundle::getHash and Models::Bundle::setHash to improve API & code clarity).