Add sequence mode to Mapillary

[gyllen]

Cache in sequences instead of tiles

[oscarlorentzon]

Related to #191 .

[oscarlorentzon]

This is supported by the current graph implementation. Needs to be exposed as a public API.

[gyllen]

@oscarlorentzon Can this be a setting?

[oscarlorentzon]

@gyllen Does setting mean a viewer options property? In that case it could. It would also have to be a public API method on the Viewer so that it can be changed at a later point in time.

Also, by supported I mean that the graph architecture allows for this to be implemented. There is still a fair amount of work to do though.

[gyllen]

@oscarlorentzon Whats your estimate?

[oscarlorentzon]

Some days.

[gyllen]

I have not heard anyone request it so lets not start anything.