[cf-launcher] Replace Digest auth with Basic

* Most WebDAV clients refuse to use Basic auth against non-SSL servers. So we
  also ensure that the WebDAV URL shown on 'help' page is always 'https://..'
cf-launcher v0.0.18

Supports Basic auth instead of digest (bug 451642)
Bug 452697 - Implement the ability to show hover info during content assist (initial stub)