Pass Xapi Params from URL to TangyForm player

[mikedawson]

When a Tangerine online survey link is opened, and xAPI parameters are appended to the URL (as per the Rustici launch parameters / RESPECT spec) then the xAPI parameters (including endpoint, actor, activity id, etc) should be available in TangyForm Player and a launched statement should be sent.

Acceptance criteria:

• Parameters have to be retrieved from the URL (not hardcoded)
• On init a launched statement will be sent

[mikedawson]

Clarification: if xAPI parameters are present in the online form URL, then xAPI statements should not be sent (e.g. no change to existing behavior).

[mikedawson]

Notes:

• Xapi parameters should be updated to match the actual spec (e.g. mailto is not a parameter, registration is a parameter).

• 'Fallback' should be removed - if xAPI parameters are present, then they should be used, otherwise, not. (avoid spaghetti scenario / unpredictable behavior)

• Xapi Actor parameter should be a JSON object - that should be added as given to any generated statement.

• Create a clean pull request that has code that implement this task (and only that). assign @mikedawson as a reviewer)

• Continue with generating xAPI statements that are in accordance with the spec.