Privacy Browser Android

This is a really good idea, although it is much more difficult to implement than may be apparent to the outside observer. Currently, Privacy Browser is set to run as a `singleTask` as described at https://developer.android.com/guide/topics/manifest/activity-element#lmode. This was done early in the development process to fix a number of bugs relating to how privacy browser may be launched by links from other apps. It works really well and makes things flow in a natural way. Having two instances of Privacy Browser side by side would require changing this to `starndard`. This could create a lot of complexity, both with how Privacy Browser interacts with other apps and how two instances of Privacy Browser interact if they are both making changes to the database backends.

I estimate that making such a change would generate several dozen bugs. This is such a desirable feature that it is worth the effort to work through all those bugs to get it working. But given the massive time involvement it would require, it is likely it will be postponed until later in the development process after features that require less work have been completed.