Refactor and cleanup in-game console to use C++ strings

Instead of storing the console text in one large buffer, it gets stored in a vector of strings. This makes the code easier to understand, as the `std::string`s now handle the buffer lenghts, instead of doing that manually and bloating the code with it, but at the cost of some performance (not noticable though). This fixes an issue where the buffer would be cut off when the total length exeeded the buffer length.
With this commit printed warnings and errors will have a red and yellow colour. It looks like this was intended, but it didn't work before, and makes `gfx_draw_string` and related functions take const strings.

src/openrct2/drawing/String.cpp

@@ -1,4 +1,4 @@
-#pragma region Copyright (c) 2014-2017 OpenRCT2 Developers
+#pragma region Copyright (c) 2014-2018 OpenRCT2 Developers
 /*****************************************************************************
  * OpenRCT2, an open source clone of Roller Coaster Tycoon 2.
  *
@@ -810,7 +810,7 @@ static void ttf_process_initial_colour(sint32 colour, text_draw_info *info)
     }
 }
 
-void ttf_draw_string(rct_drawpixelinfo *dpi, char *text, sint32 colour, sint32 x, sint32 y)
+void ttf_draw_string(rct_drawpixelinfo *dpi, const_utf8string text, sint32 colour, sint32 x, sint32 y)
 {
     if (text == nullptr) return;