Fix custom font loading on Android when using fonts that are in resource mapped directories/paths.

1: Use the CCFileUtils::fullPathForFilename function to lookup the resolved path for the font in the Android specific function, CCImage::getBitmapFromJava.

2: Remove a warning previously added in pull request 2422 (https://github.com/cocos2d/cocos2d-x/pull/2422) in CCFileUtils::fullPathForFilename in order to support change (1) above. If we pass just a system font name to CCFileUtils::fullPathForFilename such as 'Arial' (instead of a path) then it should just return 'Arial' and not generate a warning. We can't assume that when a path (or handle) given to CCFileUtils::fullPathForFilename isn't found within Cocos2dx that it doesn't exist or isn't valid. Depending on the platform there might be files or folders or handles that could be accessible to the app which might exist outside of the knowledge of Cocos2dx. The correct place to warn about missing resource files would be at the point where the resource loading itself fails; e.g if a texture or sound fails to load for example.
Merge branch 'android_custom_font_fix' of git://github.com/DarraghCoy/cocos2d-x into iss2151-customttf
fixed #2151: Custom font can't be loaded correctly if using full path of filename.
Merge branch 'master' of https://github.com/cocos2d/cocos2d-x into iss2151-customttf
fixed #2151: Commenting a log in CCFileUtils::fullPathForFilename.
Merge pull request #2557 from dumganhar/iss2151-customttf

fixed #2151: Custom font can't be loaded correctly if using full path of filename.