Add text of requirements section.

Signed-off-by: Krzysztof Opasiak <ups100@tlen.pl>
Add suitable label in nsca chapter and fix errors.

Signed-off-by: Krzysztof Opasiak <ups100@tlen.pl>
Add chapter with whole system archotecture.

Signed-off-by: Krzysztof Opasiak <ups100@tlen.pl>