Expose Resource Manager API and a default custom scheme handler implementation

[cztomczak]

CefResourceManager has a few built-in providers that map requests:

1. Content provider - maps url to string content
2. Directory provider - maps url path to directory path
3. Archive provider - maps url path to archive path (e.g. a password protected zip file)

See:

1. cef_resource_manager.h
2. cef-project/resource_manager/

Resource manager API seems to work only for HTTP urls. Additionally we could also expose a default custom scheme handler implementation that serves files from a directory. It can be based on the cef-project scheme_handler example: https://github.com/chromiumembedded/cef-project/tree/master/examples/scheme_handler

Related issues:

• Issue Scheme handler support (eg. myapp://) #50 ("Scheme handler support (e.g. myapp://)").
• Issue Example of serving content using http://myapp/ url - allows to bypass file:// protocol restrictions #465 ("Example of serving content using http://myapp/ url as a replacement for loading content using file:// protocol which has many limits")