Align and simplify install script

Change-Id: I49380522b9f22815a252e0018f211bd46f2574e7
Fix path to pa releasekey

Change-Id: I38d61732cd193c675ce9e137cd40d381a980bee8
Fix a few typ-o's

Change-Id: I5836557c0051b5b2fdf7f340925b7dbb755c1c96
Revert "build: clean up otasigcheck"

This reverts commit 5125c1da6d51f162ed0e094938659c3ec7741f6f.

Conflicts:
	tools/releasetools/edify_generator.py
	tools/releasetools/ota_from_target_files

Change-Id: I0ba16b8e601da499c2d12292bdb6759d06f26774
Add back system_items

Change-Id: I96cdbb6e2195a2b7432ca943856fa68ec567f79b