Moved global instance of style manager into the globals infrastructure.
Renamed namespace 'ocpnStyle' to 'gui'.
Refactoring: separation of functionality.
Refactoring: finding and processing style files separated.
Refactoring: reduced complexity of DefaultStyleManager's methods.
Refactoring: reading of style XML files now more robust.
Refactoring: moved classes from namespace 'gui' into the subdirectory 'gui'.
Removed unused header inclusions to FontMgr
Refactoring: wx container replaced with std::map
Refactoring: dependency to TinyXML in header reduced to forward declaration.
bug fix: windows build
Reduced dependencies with replacing header inclusion with forward declaration.