dev: core: added device files to the VFS.

All device initialise calls now add the device file that relies in the
device structure to the virtual file system. This way applications can
easily open the file and write and/or read from the device.

Signed-off-by: Michel Megens <dev@michelmegens.net>
Merge branch 'master' into dev-core

Signed-off-by: Michel Megens <dev@michelmegens.net>

Conflicts:
	drivers/core/core.c
lib: libc: added standard file operations.

Added:

	* open
	* close
	* read
	* write

These operations can be used to communicate with drivers in an
application.

Signed-off-by: Michel Megens <dev@michelmegens.net>
usart: stdio: splitted the STDIO and USART init.

Splitted the initialisation of the stdout, stdin and stderr streams from
the initialisation process of the core USART. The initialisation of
these streams is now done by the hardware driver.

Signed-off-by: Michel Megens <dev@michelmegens.net>
vfs: doc: Added docs to the vfs.

Added a module for filesystems and virtual file systems.

Hierarchy:
	- Modules
		- Kernel
			- FS
				- VFS

Signed-off-by: Michel Megens <dev@michelmegens.net>
Merge branch 'dev-core'

* File operations for stdio:

	* open/close
	* read/write

* Some generic docs.

Signed-off-by: Michel Megens <dev@michelmegens.net>

Conflicts:
	drivers/core/core.c
	fs/vfs.c
	include/etaos/stdio.h
ETA/OS 0.1.0

Signed-off-by: Michel Megens <dev@michelmegens.net>