Add "id" search for feature parity with V1 API

The V1 API "search" endpoint allows searching both on "cmd" and on "id".
V2 already supports "cmd", and so this adds "id" to make V2 on par with
V1's functionality.

Example:

    curl -H "Accept: application/json" localhost:8080/v2/apps?id=hadoop_
Refactor `search` to be more readable per feedback
Merge pull request #216 from mesosphere/v1-v2-search-parity

Add "id" search for feature parity with V1 API
Return apps matching the filter, not those that don't

This was returning the set of apps that did not match the filters. It
should return apps that match one or more of the filters.
Update README.md
Add 'Apache'; Make opening README paragraph more natural
Send full app state in PUT example

PUT expects the full state of a resource. Sending only the "instances"
attribute is misleading since the functionality is not guaranteed to
work like PATCH requests.
Unlinkify "Mesosphere" where it is close to another
Merge branch 'master' into wip-health-checks-refactored
HealthCheck primitives for new Jackson module