OFE: fixing broken partitions update logic.

[ek-nag]

Fixing the following OFE bug with this PR:

Bug report: I can consistently reproduce the following behavior:

I create a cluster with 3 partitions: a, b, c (I have been using default settings)
wait for cluster to fully deploy
edit cluster
delete middle partition ("b")
click update

Expected behavior: partition "b" is deleted, partition "a" and "c" remain
Actual behavior: generated blueprint has both "b" and "c" partitions deleted, when changes are applied to cluster only partition "a" remains.

Moving from hardcoded blueprint yaml code in the Django Python to jinja template files for better flexibility, easier development.