ARGUS-186: Updated usersync service for better handling of failures in
sending users/groups to policy admin.
ARGUS-187 trim whitespace(s) around = sign and after the property value in install.properties

Signed-off-by: Madhan Neethiraj <madhan@apache.org>
Ranger-191:Credential Provider and Policy Cache Store Unit Test Case
coverage
Argus-191: Adding missing License header
RANGER-181: moving Ranger Site (ranger.incubator.apache.org) document into ranger repo
Modified twitter account to Ranger4Hadoop
ARGUS-140 Fix some of the FindBugs problems.  (See full comments for details)

Following Problems of the class "FindBugs:Bad Practice" were fixed.  Problem text and comment about the fix are as follows:

1) Invoking System.exit shuts down the entire Java virtual machine.
- Some cases it is possible to achieve what we want achieved by setting
an existing loop control variable.
- In other cases runtime exception is thrown.

2) In com.xasecure.authorization.hive.XaHiveObjectAccessInfo.equals(java.lang.Object):
This class overrides equals(Object), but does not overridehashCode(),
and inherits the implementation of hashCode() from java.lang.Object
(which returns the identity hash code, an arbitrary value assigned to
the object by the VM).
- Added appropriate hashCode() method.
- Corresponding change equals() method to all variables are accounted
for.
- Added equals (and hence hashCode) methods to XaHiveAccessContext.

3) Return value of some system calls is ignored with potential loss of
useful diagnostic information.  Following classes were changed due to
this:
- MiscUtils
- HDFSFileAppender
- LocalFileLogBuffer
- PolicyRefresher

4) Invoking System.exit shuts down the entire Java virtual machine. This
should only been done when it is appropriate.  This lead to changes to
following classes
- XmlConfigChanger
- Crypt

5) Removed warnings for all of these files: either unused variable or
unused import.