tool_getparam: Added initial support for --next/-:

Added initial support for --next/-: which will be used to replace the
rather confusing : command line operation what was used for the URL
specific options prototype.
tool: Reworked argument parsing to use --next/-:

Follow up to commit 1a9b58fcb2 to replace the : command line option
with --next and -:.
tool: Added support to .curlrc for URL specific options

In addition to adding support for URL specific options via the command
line with --next it is now possible to specify "next" in .curlrc.