code cleanup (mainly compiler & attributes)

Add new features to README

add more signature info to UI

fix signature view in commit tree

This was a critical bug, where the signatures for each commit where displayed in the child commit. In addition to fixing this, I also verified the other displayed informations, which all display the right data.

Change short commit-hash from last to first 8 chars

Add option to hide tooltips

implement commit hash copy

Fix parent-contentChecksum mixup

Beautify Readme

pre-libostree version