Bumping version to 2.6.1, min libopenshot version to 0.2.7 (SO 21)

Adding check for empty $REQUEST_UUID on Mac builds

Merge pull request OpenShot#3263 from OpenShot/release-20200229

Release branch for openshot-qt 2.5.1 (required libopenshot version 0.2.5)

Merge pull request OpenShot#3161 from OpenShot/release-20200105

Release of openshot-qt 2.5.0 (min libopenshot version: 0.2.4)

Merge pull request OpenShot#2691 from OpenShot/release-20190320

Merge release branch into master

Merge pull request OpenShot#2134 from OpenShot/release

Release of 2.4.3 (Merge release branch into master branch)

Merge pull request OpenShot#1755 from OpenShot/feature/bump-version

Bump to 2.4.2

Bumping version to 2.4.1 (and libopenshot dependency to 0.1.9)

Bumping version to 2.4.0 (min libopenshot version 0.1.8)

Bumping version to 2.3.4 (min libopenshot version to 0.1.7)