working on applying styles for nested content that match the styles for the top level item types (observables, ttps, etc)

right now only nested ttps styles are applied.  (but the css styles for all the types are setup)

in support of #17
now added support for nested item type styles for the following types:

observable
indicator
ttp
campaign
indicdent
threat actor
exploit target

the following two item types have a class applied, but the css style is not yet defined.

event
action

This is also in support of #17