Replace SEVERITY_ERROR by RPT_SEVERITY_ERROR to avoid collision with a system definition.
Replace other SEVERITY_XXX by RPT_SEVERITY_XX for consistency.
Fix compil warnings and some other compil issues.
CHANGED: Settings are now stored in versioned sub-directories
ADDED: First-run dialog for migrating settings from a previous version
CHANGED: Settings are now stored as JSON files instead of wxConfig-style INI files
CHANGED: Color settings are now all stored in a separate settings file
CHANGED: The symbol editor and footprint editor now have their own settings files
CHANGED: Color settings are no longer exposed through BOARD object
CHANGED: Page layout editor now uses Eeschema's color scheme
Settings are now managed through a central SETTINGS_MANAGER held by PGM_BASE.
Existing settings will be migrated from the wxConfig format on first run of each application.
Per-application settings are now stored in one class for each application.
The standard DIM() macro was not typesafe as it happily deferred errors
to runtime that can be caught at compile time. Replacing it with a
generic C++11 constexpr allows for typecasting, comparison and compile
time error checking.