Alpha 5 release

- Added a very basic embark screen for entry of settlement name and map seed
- You can now manage multiple saved games via the UI, also overhauled save file format to use compression
- Improved detection of user home directory, this will cause a loss of preferences on Windows machines where My Documents has been moved from C:\Users\...
- Hard-coded "Item groups" have been entirely replaced by moddable "Stockpile groups" which determine how stockpiles and the resources management screens work
- Stockpiles now support filtering by stockpile group, item type and item material, and can also have a priority set
- Twitch integration - twitch streamers can connect their account to have their viewers automatically show up in game!
- You can now rename settlers!
- Floors now overlap underneath walls, so the transparency at the edge of wall tiles makes sense rather than showing a grey border
- Overhauled how floors overlap onto other tiles, requiring far less sprites to be created (similar to walls)
- Replaced grass floors and all floor overlap sprites
- Pressing escape in a management screen will now go back to the main game (you can also right-click in the grey areas)
- Changed settler management to show non-selected professions as greyed-out, not removed
- Settler management can now be sorted by name (new default), or unhappiness (old default)
- Added a short term memory for settlers to remember if they recently tried to place an item from inventory to a stockpile but failed, so they won't try again, to avoid getting stuck trying to use an inaccessible stockpile