Avoid NPE for anonymous admin permissions check

This avoids a potential NPE when jenkins.model.Jenkins.getUser(name) ends
up calling hasPermissions for "hudson.model.Hudson.Administer".  I ran
into this on a jenkins instance that had greenballs-plugin installed, and
READ access for anonymous users enabled.

- Verify read permissions before performing anonymous authorization checks
- Make requestURI return null if Stapler.currentRequest is null
- Make currentUriPathEquals return false if requestURI is null
Depend on latest LTS plugin version
Merge branch 'pull-10'

Conflicts:
	pom.xml