WIP: ConfigurationManager thread-safety
Start using ConcurrentConfigurationManager interface
Update ConfigurationManager with thread-safe methods

Merge ConcurrentConfigurationManager interface into ConfigurationManager
interface. This will force all clients to start using new thread-safe
ConfigurationManager methods.

DefaultConcurrentConfigurationManager is now the new "default"
ConfigurationManager. It simply adds concurrency, while delegating to
ResourceMergingConfigurationManager, which still delegates to the old
default ConfigurationManager (DefaultConfigurationManager)
Use thread-safe ConfigurationManager methods

Ensure that all users of ConfigurationManager are using "default", and
update usage to use new thread-safe methods
Update tests

Update tests to use DefaultConfigurationManager directly. Arguably,
these should be changed to use DefaultConcurrentConfigurationManager,
but they were never updated to use ResourceMergingConfigurationManager
when that was introduced, and the intent of the tests is to test the
functionality in DefaultConfigurationManager, not
DefaultConcurrentConfigurationManager
Update security version to 3.1-SNAPSHOT

Bumped minor version due to changes to ConfigurationManager interface
Delete obsolete files
Beef up comments on new ConfigMgr methods
ConfigurationManager concurrency tests

Tests for DefaultConcurrentConfigurationManager
Fix license header
Changes based on feedback

Changes from pull request feedback. The big change here was to remove
the type parameters from ConfigurationManager runRead and runWrite
methods, and ConfigurationManagerAction run method. This solution was
compiling and working on Windows, but does not compile on Linux/OSX,
most likely due to a bug in Java 1.6
Merge remote-tracking branch 'origin/master' into security-concurrency

Conflicts:
	security-realms/security-kenai-realm/pom.xml
Remove redundant synchronized method

DefaultConcurrentConfigurationManager now protects access to the save
method. No need for this method to be synchronized
Log lock timeout value
Remove unneeded synchronization

Remove synchronization around AbstractConfigurationManager clearCache
and getConfiguration. DefaultConcurrentConfigurationManager now takes
care of concurrency issues. Had to rework getConfiguration to avoid
problems with concurrent calls to clearCache.

Had to make DefaultConfigurationManager.doGetConfiguration synchronized,
as this method was relying on the
AbstractConfigurationManager.getConfiguration being synchronized
Merge pull request #29 from sonatype/security-concurrency

REVIEW: Add thread-safe access to ConfigurationManager