Standardizing Pano credentials

[achafetz]

In trying to test out pano_content(), I got an error that this is now taking new credentials, switching from session to username and password. Some of the pano_* functions take one or the other. I think we should shore this up for better consistence. To create the session, you need to add the username and password, but should we just use the session for everything else?

function	user + pwd	session	none
pano_session	X
pano_content		X
pano_download		X
pano_elements			X
pano_extract	X
pano_extract_msd	X
pano_extract_msds	X
pano_items		X
pano_unpack		X

[baboyma]

pano_session(), pano_content() and pano_elements() should now be hidden to users. They are used as internal functions where the session is a pass through. pano_items() was updated to use user/pass.

Good catch on the pano_download(). The initial design was to get all pano data items and then downlaod targeted files. We then came up with pono_extract and panoextract* as wrapper functions with pano_download() embeded - that's why it uses a session. download function can also be hidden or we will need to pass user/pass.