Fix some typos in NEWS file.

Fix typoes.

Formatting fixes:
	- Format the dates so they have the same pattern
	- Split Kernel release: items into their own subsections
	- Use "Known problems" all over
	- Indent by 4 spaces the indented lists
	- Remove extra "Bugfixes:" line
	- Indent regular bullet item by 1 space only

Signed-off-by: Elena Zannoni <elena.zannoni@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>