journal-remote: make --url option support arbitrary url
Currently, --url option supports the only form like http(s)://some.host:19531.
This commit adds support to call systemd-journal-remote as follwos:
systemd-journal-remote --url='http://some.host:19531'
systemd-journal-remote --url='http://some.host:19531/'
systemd-journal-remote --url='http://some.host:19531/entries'
systemd-journal-remote --url='http://some.host:19531/entries?boot&follow'
The first three example result the same and retrieve all entries.
The last example retrieves only current boot entries and wait new events.