Changes to improve work under windows

Added check for procps in prepare-environment
Available memory check moved to separate action
Added requirements section in README
Fixed top and free check in Cygwin

Closes-Bug: #1373655

Change-Id: I2e700602fe7bb81464975521023f4693462b4379
(cherry picked from commit 7c98912407dce20dbef759fb19719b79b4a627d2)
Merge "Changes to improve work under windows" into stable/5.1