Updating links to Istanbul from latest

Updating links to Istanbul from latest

	- Change conf.py latest to istanbul
	- Change file blob links to istanbul versions
	- Correct linking error in deployment.rst
	- Formatted Modeling to have CPS-Path as subpage to remove "CPS-Path not included in toctree" error and to retain CPS-Path in side index
	- Link to OOM user guide in deployment is currently broken but will be fixed when OOM create Istanbul branch for documentation

Issue-ID: CPS-721
Signed-off-by: lukegleeson <luke.gleeson@est.tech>
Change-Id: Ia288662af8d3adc7b08a70662fa260114a37040d