Sync ingress-specific backends and minor logging changes

[nicksardo]

Changes

• Backend service pool only syncs the list of service ports used for the respective ingress.
• Consolidate all ingress references to a single object which was deep copied.
• Changing log level of a frequently printed line from 4->5.
• Minor modifications to event handlers

Example with two ingresses in separate namespaces:

Before

# While syncing any ingress
I0205 23:03:18.031082       1 backends.go:216] Sync: backends [{30466 HTTP testing/my-echo-svc {1 0 my-http-port}} {32349 HTTP default/my-echo-svc {1 0 my-http-port}}]

After

# While syncing default/my-echo-svc
I0205 22:59:43.566574       1 backends.go:224] Sync: backends [{32349 HTTP default/my-echo-svc {1 0 my-http-port} 80 false}]
# While syncing testing/my-echo-svc
I0205 22:59:45.215794       1 backends.go:224] Sync: backends [{30466 HTTP testing/my-echo-svc {1 0 my-http-port} 80 false}]

[nicksardo]

/cc @nikhiljindal
Not yet ready for review; just giving you a heads up.

[nicksardo]

PTAL everyone

[nikhiljindal]

/lgtm.
IIUC this should speed up the controller right? Only sync the ingress that changed!

[nicksardo]

This should improve performance along with #106.