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/Gui/Dialogs/DlgProjectInformationImp.cpp

@@ -83,11 +83,12 @@ DlgProjectInformationImp::DlgProjectInformationImp(App::Document* doc,
     ui->lineEditCompany->setText(QString::fromUtf8(doc->Company.getValue()));
 
     // Load comboBox with unit systems
-    int num = static_cast<int>(Base::UnitSystem::NumUnitSystemTypes);
-    for (int i = 0; i < num; i++) {
-        QString item = Base::UnitsApi::getDescription(static_cast<Base::UnitSystem>(i));
-        ui->comboBox_unitSystem->addItem(item, i);
-    }
+    auto addDesc = [&, index {0}](const std::string& item) mutable {
+        ui->comboBox_unitSystem->addItem(QString::fromStdString(item), index++);
+    };
+    const auto descriptions = Base::UnitsApi::getDescriptions();
+    std::for_each(descriptions.begin(), descriptions.end(), addDesc);
+
     ui->comboBox_unitSystem->setCurrentIndex(doc->UnitSystem.getValue());
 
     // load comboBox with license names