Add a new system module which holds system configuration

[FlorianSW]

Currently only the host, port and protocol information, which are accessible
through the provided getter functions, but it can provide access to other
configurations and settings, too.

This improves the handling of the host, port and protocol part of a base url,
which was currently handled by a single configuration variable, only. With this
it was unclear, what the configuration holds and what is expected (with protocol,
or without, with port or without, and so on). The configuration also slightly
changed. The system object know provides a separate way for specifying the base
url with the new options:

• protocol: The protocol of the "public" accessible URL for this service (e.g. http
  or https)
• host: The host- or domain name from which this service is accesible, e.g. localhost
  or example.com
• port: The port over which this service is accesible, e.g. 80 or 443.

This also fixes #45 by using the new getBaseURL() method of the System class to retrieve
the base url of the service and appends the path to that, instead of a hard-coded URL.

[digitaldan]

Very cool btw, much better than passing around the config json, reviewing now.

[digitaldan]

@marziman FYi this will break current configurations until they update their config, which I'm ok with, just something to be aware of.

[FlorianSW]

Interesting, I used github's conflict resolution teh first time :P If the separate merge commit isn't ok (which I would totally understand), I'll squash both commits, just leave a note :)

@digitaldan Hmm, it shouldn't, I tried to implement an on-the-fly migration in the constructor of System to not break current configurations. Do I miss something, or have I implemented it wrong? :)

[digitaldan]

i mean anyone who is implementing their own cloud install will need to add host/port/protocol to their config after this PR is committed

[FlorianSW]

Oh, yes, you're right, however, I'm totally fine with it. From what I understand, the configuration options in the base section are required system settings. I would expect the system start to fail if the settings aren't set :) But thanks for the note, I hope that's ok for all users.

[digitaldan]

Sorry, I see you do support backwards compatibility here https://github.com/openhab/openhab-cloud/pull/81/files#diff-5c350865b90e8c9c7f2b316f9c84f74fR17 , but when I tried it with an existing configuration the links in my emails looked like this "mydomain.com://443:null/lostpasswordreset?resetCode=51535fe0-456d-11e7-8d3b-ab18cbf0bfa1"

[FlorianSW]

Oh damn... I assume you have the following in your baseurl setting:
"mydomain.com:443"
right? This will obviously fail, because the protocol is missing. Let me check, if we can workarount this :)

[FlorianSW]

@digitaldan I accidently[1] used git commit --amend and was too lazy to split the commit manually, so I force pushed. The change happened in 3e4a3a5#diff-5c350865b90e8c9c7f2b316f9c84f74fR19 and the lines after. I hope that's ok :)

[1] In another project where I'm mostly active, we're using gerrit, where a change is updated by amending the commit, and my fingers were faster as my head :)

[marziman]

@digitaldan:
Thanks. I think it is ok to improve the config by this way. We might add this to docu.
@FlorianSW: Yes protocol was not there before, since it was URL:PORT

[digitaldan]

LGTM

[FlorianSW]

Thanks! :)