User-defined keystore and truststore properties.

5 properties were added to the gitblit.properties file. This allows a user to configure an existing SSL certificate GO distribution.


### start of new properties
server.useGeneratedSSLCertificate =  true

##### ignored if useGeneratedSSLCertificate = false
server.caConfig =

##### ignored if useGeneratedSSLCertificate = true
server.caRevocationList =
server.storeLocation = 
server.trustStoreLocation =