Change trees to open at current progress marker by default

**Issue by [chaorace](https://github.com/chaorace)**
_Friday Mar 31, 2017 at 02:51 GMT_
_Originally opened as https://github.com/CQUI-Org/cqui/issues/451_

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Currently, the tech/civic trees always default to opening positioned on the far left. This isn't a major issue because trees will keep your scroll position in memory. However, it's rather annoying to have to scroll through it all on the first open after loading a save

Start by locating the tech and civic tree UI entry points and tracing how their scroll position is initialized when a save is loaded. Confirm the desired behavior by opening each tree after loading a save: it should begin at the current progress marker rather than the far left, while preserving existing scroll-memory behavior.

Written by the indexing model from the issue text.