[doc] optimized images

doc/eva/gui-images/eval-acsl.png

doc/eva/gui-images/gui-callstacks-annotated.png

doc/eva/gui-images/gui-callstacks.png

doc/eva/gui-images/gui-loop-to-unroll.png

doc/eva/gui-images/gui-red-alarms-panel.png

doc/eva/gui-images/gui-red-values.png

doc/eva/gui-images/gui-side-panel.png

doc/eva/gui-images/gui-values-annotated.png

doc/eva/gui-images/gui-values.png

doc/eva/gui-images/gui1.png

doc/eva/gui-images/gui2.png

doc/eva/gui-images/gui3.png

doc/eva/gui-images/gui4.png

doc/eva/gui-images/gui5.png

doc/eva/gui-images/studia.png

doc/images/logo-frama-c.jpg

doc/images/logo_8bits.png

doc/userman/gitlab-bug-report.png

doc/userman/gitlab-login.png

doc/userman/gui-main-window.jpg