Add audit logging of login success or failure

Authentication success or failure is appended to IIS logs.
The commit detail template adjusted so the link creation detects an empty/null string. Browser displays (null) instead of the empty text
Merge pull request #147 from voloda/Issue#144

The commit detail template adjusted so the link creation detects an empt...
Refactored Git command execution in prepation for "hooking" it for receive-pack commit analysis
Basic receive-pack handling wrapper classes added. Not yet fully functional.
Added "AuditPushUser" configuration option on the repository.
Added a more sophisticated receive-pack parse that recongizes multiple ref lines. Added unity decorator support.
adjusted exception wording
put in a basic implementation of auditing push user to git notes associated with the commit.
Added commit notes display to commits page
Push uer auditing is now only performed when "Audit
 option is turned on for that repository
Made receive pack hook "post" call durable by persisting the pack to database an executing based on that data.
Moved time configuration into constructor parameter
fixed git2 NativeBinary reference. publish was broken otherwise.
stopped using default notes user signature because it doesn't work in all cases
Fixed AddAuditPushUser.cs SQL Server script. Removed word "column" from alter statement.
Merge pull request #145 from dnadle/master

Add audit logging of login success or failure
Merge pull request #143 from stanshillis/master

Record username of the user that pushed commits to the server
Removed null check from commit view as it is already in model