This patch adds some documentation for the context management library.
It mainly covers the design at a higher level, with more focus on
the cold boot and warm boot entries as well as the operations
involved during context switch. Further it also includes a section
on feature enablement for individual world contexts.
Change-Id: I77005730f4df7f183f56a2c6dd04f6362e813c07
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
