Update charter based on F2F discussions during TPAC

[tidoust]

The following changes were made:

• Completion dates were updated to reflect current implementation plans, and the dependency on Open Screen Protocol was noted in particular to justify the completion date of the Presentation API in Q4 2019.
• The intent to work on a testing API was noted in Test suite section. The text gives freedom to the Working Group to put that testing API in the current drafts or in Level 2 specs.
• The reference to the Network Service Discovery API was dropped
• The "boilerplate" text was updated to match latest template, in particular in the coordination section (I did not try to inject all template updates though, so as to keep diff minimal)
• The liaisons section was adjusted.

I note that the Charter still says that mandating protocols is out of scope of the Working Group. In other words, as things stand, the Working Group cannot add text such as "the user agent MUST support the Open Screen Protocol" to the Presentation API and Remote Playback API.

[anssiko]

@tidoust, thanks for the update. As for the normative changes, this looks good to me per F2F agreement. I submitted some comments for clarifications.

When do you want to ship this to W3M latest?

@mfoltzgoogle, here's the HTML diff to ease the review.

[tidoust]

Thanks for the comments, @anssiko. I integrated them.

Regarding shipping to W3M, the sooner the better. The week of the 4 December at the latest. Typically, issuing a call for consensus end of this week within the group would be good.

[anssiko]

I sent a CfC with a DL of 28 Nov. I suggest we integrate further proposed changes from the group to this branch prior to merging.

[tidoust]

Noting PR #7 which proposes updates to this pull request.

[tidoust]

Changes proposed in PR#7 have now been included in this pull request. I also added the suggested "test as you commit" policy text to the Deliverables section, as discussed in #2.