less: introduce less variables and use them to control the logo styling This will make it easier to customize the logo. Also introduce kallithea-variables.less, intended to contain various values that easily can be modified to change most of the styling. Original patch modified by Mads Kiilerich to just change the styling method without changing the look.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.