Discourage fee sniping with nLockTime
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
libbitcoinconsensus: Add pkg-config support
[Qt] fix missing plural form for a string in sendcoinsdialog

- this was reported on Transifex by pryds (Thank you!)
[Qt] change some strings to reflect name change to Bitcoin Core
[Qt] fix a translation that occurs 2 times but was a little different
Test unexecuted OP_CODESEPARATOR

OP_CODESEPARATOR is an actual executed instruction, not a declarative
thing, so if it's wrapped in an OP_IF it can be turned off.

Using this to implement Rivest's Paywords is left as an exercise for the
reader.
Revised translation process doc
Add /rest/headers
minor fix on script test data docs
Merge pull request #5482

87e8e1c minor fix on script test data docs (Manuel Araoz)
Remove references to X11 licence
Merge pull request #5444

f676c80 Add /rest/headers (Pieter Wuille)
Merge pull request #5219

31aac02 Qt: new icons (Jonas Schnelli)
[RPC-TESTS] ability to run single test manually

adds possibility to run ./qa/pull-tester/rpc-tests.sh <TESTNAME>
Qt: HiDPI (retina) support for splash screen

- remove splash screen images (reduce binary size)
- dynamicly draw splash screen with available icon.
- remove testnet icon
- dynamicly colorize testnet icon
Qt: Go back to using QIcon functionality for scaling
resize tray icon because a 1024x1024 icon won't show in ubuntu (bug)
Merge pull request #5228

ac23394 resize tray icon because a 1024x1024 icon won't show in ubuntu (bug) (Jonas Schnelli)
8e76ca0 Qt: Go back to using QIcon functionality for scaling (Wladimir J. van der Laan)
54f2571 Qt: HiDPI (retina) support for splash screen (Jonas Schnelli)