NEXUS-5727: Prevent multiple creation of thread.

Shiro 1.2.1 suffers from a concurrency issue that causes
multiple session validation threads to be lazily
created upon first request for a session. We saw
this on OSO Nexus instance for example, where we
had 5 such threads concurrently sweeping for stopped
sessions.

This applies a workaround usable with Shiro 1.2.1.
The workaround is to "preinstall" the session
validating thread, so no "lazy" creation
(that is not thread safe) will happen.

Issues:
https://issues.sonatype.org/browse/NEXUS-5727
https://issues.apache.org/jira/browse/SHIRO-443
Merge remote-tracking branch 'origin/master' into nexus-5727-session-validation-thread
NEXUS-5727: Simplified the fix.
NEXUS-5727: Expanding module test

Checking for properly set cache too
Merge remote-tracking branch 'origin/master' into nexus-5727-session-validation-thread
Merge remote-tracking branch 'origin/master' into nexus-5727-session-validation-thread
NEXUS-5727: Applied Stuart's advice

Removed the clumsy setSessionDAO method
from fixed classes that were needed only to
"trigger" the member injection.

Using bind.toConstructor works without this.
explain what nexus.version is for, and why project.version used here is safe
add enforce-prerelease profile to help do the job the release plugin would have done.
update docs
Fix expected number of roles to include also P2 contributed roles

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Upload using a path to avoid nexus bug of nexus trying to remove ".nexus/attributes" when trying to remove root

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Merge branch 'master' of github.com:sonatype/nexus-oss
move sniff profile above ide profiles
add DM for capabilties plugin jar
hook up ldap plugin
add DM for ldap-common
add buildsupport/bouncycastle
note about rename/move
add selenium deps