Add mbcn data

[eyvorchuk]

Changes

• Adds mbcn_cmip6.py and mbcn_canesm5.py to pdp/portals
• Adds aforementioned portals to main.py
• Adds aforementioned portals and other portals to pdp.rst
• Adds downscaled_cmip6_multi and downscaled_canesm5_multi to raster.rst
• Adds cmip6_mbcn_app.js and canesm5_mbcn_app.js to pdp/static/js and to canada_ex_map.js

Resolves #283

Checklist

• [ ] Full integration tests are passing locally No updates to tests
• [x] Docs have been updated to reflect the changes

[eyvorchuk]

Were these code changes in the demo I looked at a couple days ago?

Yep. The only thing I added since you looked at the demo was the doc updates.