API for setting targeting (AdEx Profile) preferences: AIP#15

[Ivshti]

See https://github.com/AdExNetwork/aips/issues/15

We need an API that would allow the profile.adex.network origin to set preferences (targeting tags in grouped format) in the localStorage

This should also set new targeting variables as per targeting and bidding (originally AIP31)

Variables to be added to the AdView and the spec:

• adView.hasCustomPreferences
• adView.preferredCategories
• adView.excludedCategories

Excluding campaigns will not be a part of the targeting system, it will be handled separately