Introduce unit test for FontCache
CMakeLists: Remove resources file

* This file has no use.
ResourceFile: Move RESOURCE_TYPE enum inside class to prevent collision

* This prevents a namespace collision with an enum in the UIWidget
header file.
Fix MSVCPP compile err
Fix compile err (not found) for Template unit test
Fix WindowsOS system fonts path
IFont: Rename typedefs -- RawPtr -> raw_ptr && SharedPtr -> shared_ptr

* This is to help ease the future merger of feature/GUI.
travis-ci: Add build test for OS X
Update third-party deps list -- using modified SDL2_ttf.framework
travis-ci: Add building & exec of unit tests
GUI engine

This branch, 'feature/GUI', has been rebased (squashed), in order
to ease merging branch 'feature/FontResource' onto it. For the
complete history of 'feature/GUI' up to the point in time before
rebasing, see branch 'feature/GUI-historic'.
UIWidget: Integrate use of nom::Font into GUI branch
Copy font resources for VBoxLayout unit test when on WindowsOS

* This partially fixes the failing of the test for this platform.
Introduce unit test for FontCache
Revert NOM_DISABLE_GFX_LOG_TRACE macro

* The macro got lost somewhere in all the merging as of late. Oh well!
VBoxLayoutTest: Fix the test failures with layout spacing
examples/fonts: Fix crash when font is NULL
FontCache: Restructuring of init (introduce static helper interfaces)

* SDLApp: Removal of fonts_ class variable & getter method; the global
nom::SystemFonts interface replaces access to it.
* SDLApp: Font enumeration relocated to
PlatformSettings::enumerate_fonts.

* ResourceCache: Explicit clear on resources container upon
destruction.
FontCacheTest: Change ResourceCache type to Font
UIWidget: Introduce font setter for Font raw pointers.

* Font: Introduce DEFAULT_FONT_SIZE (12 pt) const var.