[FIXED JENKINS-23526] Tolerate 'null' result when used creatively

- Replaces thick shadow with a fuzzy shadow.

- adds more padding

- adds a pointer cursor to indicate the items are clickable.

Previously the inputs would bleed behind the help text. They were still
clickable but this is not a desirable visual effect.

[FIXED JENKINS-23434] Sort NullSCM first

[FIXED JENKINS-14264] For logs >200Kb, just show two <t:task>s without nesting, for proper interoperability with the context menu.

- Swap out black borders for gray ones

- Add rounded corners to form areas

[FIXED JENKINS-23191] f:radio is not databinding-aware and does not correctly handle multiple configuration sections unless you make it.

[JENKINS-23191] Cannot reproduce problem in HtmlUnit test, but can at least guard against other regressions.

[FIXED JENKINS-23094] Use POST to start slave agent

[FIXED JENKINS-23361] Add CLI commands to add jobs to and remove jobs from views

Plugins like github-oauth-plugin implementing SecurityRealm need to call
these methods in security lifecycle events.