Revert "Change alphasPower to Short_t to fix ROOT type conversion"

This reverts commit c0ed12ff0b5c2f8a529effbf092f67cecc9a3d00.

Conflicts:
	SelectorCommon.h
	SelectorReader.h
	root-analysis.h
Merge branch 'master' of https://bitbucket.org/Vayu/root-analysis