Improve documentation

[MansMeg]

• Give a more clear example that the output from pxweb_interactive() is a list with slots
• remove interactive_pxweb from the vignette and make depricated
• be more clear in documentation and with examples that the output from pxweb_get is not the same output as from the pxweb_interactive.

[MansMeg]

• Also clarify that pxweb_interactive default spits out all values that are currently available. You can change this to "\star" to get all values currently available.