Porting master/detail pattern to the rest of the console

Implemented the drilldown pattern per [NEXUS-7612](https://issues.sonatype.org/browse/NEXUS-7612). This is a huge change, so I fully expect some kinks.

In particular, you’ll notice that singleton buttons and tabs on detail panes look strange, per the screenshot below:

![routing - sonatype nexus 2014-11-25 10-43-02](https://cloud.githubusercontent.com/assets/186715/5189105/f70980c6-748f-11e4-8b09-1e29890d1fe5.png)

I think this is fine for now, for a couple of reasons:

+ For detail panes with a single tab, I recommend we use an [h3 instead of a tab](https://issues.sonatype.org/browse/NEXUS-7758) to label the section.
+ We have a [plan](https://issues.sonatype.org/browse/NEXUS-7709) to redesign tabs. This will give them a background treatment similar to that of grid rows (below), which will result in better separation between the action buttons and the content.

![repositories](https://cloud.githubusercontent.com/assets/186715/5189193/7fdcc1d8-7490-11e4-94e5-70257b0c6cce.png)

The following admin features have been converted to the drilldown pattern:

*Repository*
- Repositories
- Routing
- Targets

*Staging*
- Profiles
- Rules

*Security*
- Privileges
- Roles
- Users
- LDAP
- SSL Certificates

*System*
- Capabilities
- Plugins
- Trusted Keys
- Tasks
- Templates
Drilldown is a framework. Master/detail is an implementation of that framework.

The drilldown framework takes as input an arbitrary number of panels, and provides a breadcrumb and a method for switching between panels. It doesn’t have insight about when to switch between panels, or how to update the contents of those panels.

The masterdetail implementation takes a grid panel and a tab panel, and implements the event handlers for updating data and switching to the detail panel when a row is clicked.

In the same way, wizards could potentially be an implementation of the drilldown framework. That’s my thinking, anyway.