various fixes towards LegacyCapture

- sniper using Captures, but churches using LegacyCapturable
- unable to parse CaptureThreshold/SabotageHPRemoval from yaml
- not firing up INotifyCapture and breaking:
  * sniper transforming the church on capture in ra
  * proc not giving away it's contents in cnc
remove SupportPowerBin from observer widget

fixes #3444
Merge pull request #3469 from Mailaender/unarm-observers

Removed SupportPowerBin from Observer Widget
Merge pull request #3465 from Mailaender/legacy-capture-fixes

Various fixes towards LegacyCapture
remove unused icons
integrated R8Reader with OpenRA file system

* removed R8Reader from Utility
* removed console spam from R8Reader
moved the r8 conversion to sequences

closes #2566