Base: simplify UnitsSchemas management

Fixes: Maintaining schemas is difficult and error-prone

- Facilitate easy schemas add, remove, change, etc.
- Remove 14 files containing approx 2,190 lines of if/else code and data
- Place data in one file (UnitsSchemasData.h) using a normalized structure (including special functions)
- Isolate and simplify data operations (code)
- Remove schemas enum to keep data independent of code
- Separate responsibilities: Specifications, data, schemas, schema
- Add schema data 'isDefault'
- Add schema data name
- Prefer algorithms to raw loops
- Add schemas unit tests
- Tweak quantity unit tests

src/Base/Quantity.cpp

@@ -64,7 +64,7 @@ int QuantityFormat::defaultDenominator = 8;  // for 1/8"
 QuantityFormat::QuantityFormat()
     : option(OmitGroupSeparator | RejectGroupSeparator)
     , format(Fixed)
-    , precision(UnitsApi::getDecimals())
+    , precision(static_cast<int>(UnitsApi::getDecimals()))
     , denominator(defaultDenominator)
 {}
 
@@ -256,14 +256,15 @@ std::string Quantity::getUserString(double& factor, std::string& unitString) con
 std::string
 Quantity::getUserString(UnitsSchema* schema, double& factor, std::string& unitString) const
 {
-    return schema->schemaTranslate(*this, factor, unitString);
+    return schema->translate(*this, factor, unitString);
 }
 
 std::string Quantity::getSafeUserString() const
 {
     auto userStr = getUserString();
     if (myValue != 0.0 && parse(userStr).getValue() == 0) {
-        userStr = fmt::format("{} {}", myValue, getUnit().getString());
+        auto unitStr = getUnit().getString();
+        userStr = fmt::format("{}{}{}", myValue, unitStr.empty() ? "" : " ", unitStr);
     }
 
     return Tools::escapeQuotesFromString(userStr);