Create a script to generate initial release note

We need a script which generates initial version of release note:

• release note will be written in .rst files like quips (https://codereview.qt-project.org/gitweb?p=meta/quips.git;a=tree)
• Content is written by using markdown language (like quips:https://codereview.qt-project.org/gitweb?p=meta/quips.git;a=blob;f=template.rst;h=f7c1b8cbde64ab6081d7a6c5f7343046de296ba5;hb=HEAD)
• There will be 3 sections in release notes
  • 1. Most important changes since previous release from same series (or from previous minor one in case of .0 release). This is fetched from commit message's [ChangeLog] -tag
  • 2. Bugs fixed in the release. This is fetched from commit message's Fixes -tag
  • 3. Contributors for the release. This is fetched from gerrit commits and contributors are listed in alphabetical order (by last name)