Merge bitcoin-core/gui#556: refactor: Make BitcoinUnits::Unit a scoped enum

0e5dedbc9e qt/wallettests: sort includes (William Casarin)
0554251d66 qt: Skip displayUnitChanged signal if unit is not actually changed (Hennadii Stepanov)
ffbc2fe459 qt, refactor: Remove default cases for scoped enum (Hennadii Stepanov)
152d5bad50 qt, refactor: Remove BitcoinUnits::valid function (Hennadii Stepanov)
aa23960fdf qt, refactor: Make BitcoinUnits::Unit a scoped enum (Hennadii Stepanov)
75832fdc37 qt: Use QVariant instead of int for BitcoinUnit in QSettings (Hennadii Stepanov)

Pull request description:

  This is a rebased version of #60

  Since Qt 5.5 there are [means](https://doc.qt.io/qt-5/qobject.html#Q_ENUM) to register an enum type with the meta-object system (such enum still lacks an ability to interact with [QSettings::setValue()](https://doc.qt.io/qt-5/qsettings.html#setValue) and [QSettings::value()](https://doc.qt.io/qt-5/qsettings.html#value) without defined stream operators).

  In order to reduce global namespace polluting and to force strong type checking, this PR makes BitcoinUnits::Unit a scoped enum (typedef BitcoinUnits::Unit BitcoinUnit;).

  No behavior change.

ACKs for top commit:
  jonatack:
    ACK 0e5dedbc9e, review and debug build of each commit after rebase on current master, lightly tested running the GUI, changing units a few times, and verifying persistence after restarting
  promag:
    Code review ACK 0e5dedbc9e

Tree-SHA512: 39ec0d7e4f0b9b25be287888121a8db6b282339674e37ec3a3554da63a9e22d6fe079e8310ca289b2a0356a19b3c7e55afa17d09dd34e0f222177f603bb053a3

src/qt/transactiontablemodel.cpp

@@ -5,6 +5,7 @@
 #include <qt/transactiontablemodel.h>
 
 #include <qt/addresstablemodel.h>
+#include <qt/bitcoinunits.h>
 #include <qt/clientmodel.h>
 #include <qt/guiconstants.h>
 #include <qt/guiutil.h>
@@ -232,7 +233,7 @@ public:
         return nullptr;
     }
 
-    QString describe(interfaces::Node& node, interfaces::Wallet& wallet, TransactionRecord *rec, int unit)
+    QString describe(interfaces::Node& node, interfaces::Wallet& wallet, TransactionRecord* rec, BitcoinUnit unit)
     {
         return TransactionDesc::toHTML(node, wallet, rec, unit);
     }