support a combo security scheme in TD and per property/action/event security scheme

[VigneshVSV]

Once we support more security schemes apart from basic auth, the combo security scheme would be important if the user specifies multiple security schemes.

By default, specifying a list of security schemes ANDs the security procedure. However, normally one would require only one of the security scheme if multiple are specified or a specific combination of the schemes. This needs to be reflected in the TD.

This issue can be picked up only after we support some more security scheme. This is a tracking ticket.

Rough steps:

• if multiple security schemes are specified, by default, OR them instead of ANDing them
• accept a input argument to the HTTP server where the combo security scheme is specified. define the API as well. hopefully this is preagreed before working on the issue.
• edit add_property, add_action and add_event so that a security scheme per interaction affordance is accepted. Populate this correctly in TD as well and enforce it in the same way
• add tests and docs