GlideinWMS

Add some documentation in http://glideinwms.fnal.gov/doc.prd/components/tools.html
At least the help message and an example.
Maybe some explanation (possible errors, glideins could be removed by the Factory)

manual_glidein_submit changes:
- what about calling is glidein_manual_submit or gwms_manual_glidein_submit? To make it easier to find the GWMS tools
- when there is an error in the parameters should print also the usage/help string
- this is installed w/ the Factory, what about making the local hostname the default collector?
- when an invalid req-name is provided, would help if it printed a list of valid names (condor_status any -constraint '(MyType=="glideclient")' -pool <wms_collector> -af name)
would be useful if it checks that the user can submit or if it prints a warning if it is not running as the gfactory user. The switchboard errors are not helpful in understanding what happens
- if the program is invoked right after a restart (before the key is updated in the classad) probably will get a "glideinwms.factory.glideFactoryCredentials.CredentialError: Symmetric key extraction failed." It should either catch the exception and print a message sying to wait or add that in the documentation