Add support for configuring active/inactive state of kerberos plugin

Add support for configuring active/inactive state of kerberos plugin
independently of the spring-security-core plugin. This allows an
application to have spring-security-kerberos installed, but configured
as inactive. This is consistent with the spring-security-ldap plugin
and the implementation is identical.
Correct comment
Merge pull request #1 from selera/master

'Active' config flag for spring-security-kerberos
classpath updates
update to Grails 2.0.4 and release 2.0.3
license updates
doc update
cleanup
dropped support for 1.2
GPSPRINGSECURITYKERBEROS-4 and GPSPRINGSECURITYKERBEROS-6
GPSPRINGSECURITYKERBEROS-2
0.2-SNAPSHOT release
update to latest release plugin
GPSPRINGSECURITYKERBEROS-7
Update SpringSecurityKerberosGrailsPlugin.groovy

change the package import corresponding to package naming changes in spring-security-core 2
http://grails-plugins.github.io/grails-spring-security-core/docs/manual/guide/newInV2.html
Merge pull request #2 from MatrixCrawler/patch-1

Update SpringSecurityKerberosGrailsPlugin.groovy
deleted unused files
changed package to be consistent with the core plugin
updated to use spring-security-core:2.0-RC2
update for package change in Spring Security 3.2