(TK-10) Cleanup endpoint saving

Cleanup endpoint savings as per suggestions on the PR.
Change definition of state in let statements to (:state s).
Use update-in instead of assoc when updating state atom.
(TK-10) Use keywords to indicate type

Change from using defined constants to using keywords to indicate
the type of endpoint information. Also fix use of update-in.
(TK-10) Add additional servlet info

Add :servlet field to the servlet endpoint map, which contains
the type of the servlet.
(TK-10) Merge tests/change proxy keys

Merge the two tests testing get-registered-endpoints.
Change the names of the proxy keys to be more helpful/accurate.