[Qt] add messages when handling local payment request files

- important for the open URI dialog to give users feedback
  when a file is invalid etc.
Store orphan blocks in serialized form
Tweak linearize.py to give more flexibility

Add the ability to start at a non-zero height, and allow for appending to
an existing file.
Merge pull request #3518 from Michagogo/linearize-start-value

Tweak linearize.py to give more flexibility
build: fix MacOSX build after ec41342

Fix regression introduced in ec41342.

Also use a less ugly solution, by defining the value of
`MOC_DEFS` in the configure script instead of `Makefile.include`.
Merge pull request #3524

67d60f7 build: fix MacOSX build after ec41342 (Wladimir J. van der Laan)
src/leveldb/Makefile is ignored?

remove the "-" in leveldb-* to include src/leveldb/Makefile
qt: use series of pngs for spinner

Use a series of .png frames for the spinner instead of a .mng.
`mng` is an obscure image format and is not built by default into Qt5.

This appears to improve the crispness of the spinner as well.

Does not noticably increase the size (still ~27k) and the code
is not more complicated either.
qt: Minor message updates

Used sending/receiving addresses -> Sending/receiving addresses
Previously requested payments -> Requested payments (idea from @cozz in #3521)
Merge pull request #3374

bd70562 [Qt] add messages when handling local payment request files (Philip Kaufmann)
Merge pull request #3528

66a8829 qt: Minor message updates (Wladimir J. van der Laan)
qt: English translation update
Merge pull request #3532

f087ce8 qt: English translation update (Wladimir J. van der Laan)
Merge pull request #3516 from sipa/serorphans-head

Store orphan blocks in serialized form
Merge pull request #3525

15570cc src/leveldb/Makefile is ignored? (harry)
Merge pull request #3526

f10b2d7 qt: use series of pngs for spinner (Wladimir J. van der Laan)
qt: Update copyright year in about dialog to 2014
qt: Update remaining "The Bitcoin Core Developers"