Implement OS interface about v7

[cpq]

• Rename File to Os (python-like)
• Add Os.system()
• Add Os.stat()
• Add Os.rename()
• Add Os.info() - get OS information

[imax9000]

What are the use cases for OS interface? Should it be just a dumping ground for things that don't fit into other interfaces (like Socket) and are offloaded to the hosting OS?

I assume that if we're running without an OS (on bare hardware) it's up to the vendor to implement particular methods.

[cpq]

For the start, file operations and starting processes (if there is an OS) is enough. And yes, Os would be a dumping ground. Main APIs that we anticipate are hardware (e.g. UART, SPI) to collect data from hardware, and networking (Fossa) to transmit that data outside.

[imax9000]

How about replacing stat with exists, readable and writable? Mapping struct stat to JS is going to be awkward.

[cpq]

+1 for suggested rename