Add option to set the domain of the SOI cookie

[cphilleo]

The Problem

Multiple sites on sub-domains would like to share consent, e.g. sub1.example.com, sub2.example.com, sub3.example.com. This can be achieved by using the POI feature and specifying a common domain such as consent.example.com however there is overhead of at least 20K per page load to use POI.

Proposal

Since subdomains can set a shared cookie on the parent domain, it's more efficient to allow the SOI cookie to be set on the parent domain, and then be shared by all subdomains. This would be a form of group consent.

This pull request adds an option to set the domain to be used for the SOI cookie. Setting the cookie to an invalid non-parent domain results in no cookie being set.

[coveralls]

Pull Request Test Coverage Report for Build 937

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 351 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.05%) to 31.462%

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Files with Coverage Reduction	New Missed Lines	%
dist/oil.bundle.js	351	31.46%

Totals
Change from base Build 936:	0.05%
Covered Lines:	1138
Relevant Lines:	2972

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💛 - Coveralls

[alexgit2k]

Good suggestion, I would need the same. Can you please resolve the error.