Qt: new icons

- flat and b/w icons seems to be the new trend
- support for HiDPI/retina
- change icon sizes
- fix assets-attribution.md
- removed unused icons
[Qt] the RPC Console should be a QWidget to make window more independent

- fix issue #5254
Do all block index writes in a batch
Add /opt/local/include/db48 only if it exists.
Move SendMoney() to rpcwallet.cpp.
Use RPC_INVALID_PARAMETER instead of RPC_WALLET_ERROR for invalid amount.
No return at the end of void function.
Make several small string fixes in linearize-data.py

- Add a space after the fixed string prepended to file names when input or
  output file changes
- Clarify the error message when the genesis block is not found in the
  hash list (...why do we have this at all?)
Remove genesis block hash from error
Remove coinbase-dependant transactions during reorg.

This still leaves transactions in mempool that are potentially
invalid if the maturity period has been reorged out of, but at
least they're not missing inputs entirely.
Remove txn which are invalidated by coinbase maturity during reorg
Make CTxMemPool::check more thourough by using CheckInputs
Make CTxMemPool::remove more effecient by avoiding recursion
RPC-test based on invalidateblock for mempool coinbase spends
contrib: show pull # in prompt for github-merge script
Merge pull request #5449

6e6a36c contrib: show pull # in prompt for github-merge script (Wladimir J. van der Laan)
[REST] /rest/block response with full tx details

- rest block request returns full unfolded tx details
- /rest/block/notxdetails/<HASH> returns block where transactions are only represented by its hash
[REST] added /rest/block/notxdetails/<hash> into REST-interface.md documentation
[REST] JSON output: remove block infos from tx details if it is nested in block
Merge pull request #5395

4c69ebe Add /opt/local/include/db48 only if it exists. (Pavel Janík)
Merge pull request #5399

4be639e Use RPC_INVALID_PARAMETER instead of RPC_WALLET_ERROR for invalid amount. No return at the end of void function. (Pavel Janík)
b93173d Move SendMoney() to rpcwallet.cpp. (Pavel Janík)