Restore ACTIVE_TEXT_COLOR

Use ACTIVE_TEXT_COLOR instead of DEFAULT_TEXT_COLOR, as in Fremantle version.

In Diablo, ACTIVE_TEXT_COLOR is defined as "EmpTextColor" instead of
"ActiveTextColor".

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch diablo
# Your branch is ahead of 'origin/diablo' by 1 commit.
#
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#	modified:   src/SeriesFinale/gui.py
#	modified:   src/SeriesFinale/lib/constants.py
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
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#	build-stamp
#	build/
#	configure-stamp
#	debian/files
#	debian/seriesfinale/
#	src/SeriesFinale/__init__.pyo
#	src/SeriesFinale/lib/__init__.pyo
#	src/SeriesFinale/lib/constants.pyo
