1.5.1: Merge pull request #270 from foosel/fix/deprecated_flask_imports

This version comes with some new feature and some bug fix, the release is not in a good shape but needed to work with the new version of octoprint 1.4.1

fixes #195
Merge pull request #1 from rlogiacco/fix/201
Merge pull request #2 from rlogiacco/fix/195
Merge pull request #198 from rlogiacco/fix/195
Merge pull request #202 from rlogiacco/fix/201
Merge pull request #203 from giloser/master
Issue #181: notification for user interaction requests
Merge pull request #3 from ZeGuigui/PauseUserEventNotify
Fix - Remove double percentage
Update to manage MultiCam
Fixed image mirroring
Merge pull request #242 from f4nu/master
Merge pull request #235 from giloser/master
Merge pull request #226 from chatelao/patch-1
Merge pull request #224 from alpxp/master
drops octoprint generated hash code from telegram file identifier
Merge remote-tracking branch 'upstream/master' into fix/236
Merge pull request #245 from fabianonline/revert-224-master
Merge remote-tracking branch 'upstream/master' into fix/236
Merge pull request #246 from rlogiacco/fix/236
Merge pull request #270 from foosel/fix/deprecated_flask_imports