use salted sha512 instead of unsalted md5 for storing passwords
add test to assure new hash method is used
reintegrate md5 password check for backwards compatibility
Merge branch 'master' into saltedsha
Merge branch 'saltedsha' into develop

Conflicts:
	Bonobo.Git.Server/Properties/AssemblyInfo.cs
remove obsolete todos
extract PasswordService
remove test dependency to EF by using an update hook instead of db context
+password upgrade releated test cases
fixed test cases
Merge pull request #118 from embix/saltedsha

add backwards compatible upgrade of method to store hashed passwords