Adds ability to generate graphs for custom areas

This commit adds the ability to generate individual PNG and SVG graphs
for custom areas, defined as the union of several "Àrees Bàsiques de
Salut" (ABS) in the config/customAreas.php file.

Change-Id: I27f34b4a8f520a38c55eed224554b470c5ba2938
diff --git a/cron/generate.bash b/cron/generate.bash
index 8e0b569..201740b 100644
--- a/cron/generate.bash
+++ b/cron/generate.bash
@@ -1,6 +1,14 @@
+# Create the output folder if it doesn't exist
+rm -rf ../output
+mkdir -p ../output
+# Generate graphs for the Catalonia health areas
 php generateData.php
 gnuplot generateGraphs.gnu
-mkdir -p ../output
 mv /tmp/covid19graphgenerator-output.png ../output/graph.png
 mv /tmp/covid19graphgenerator-output.svg ../output/graph.svg
+# Generate graphs for each custom area defined in
+# config/customAreas.php
+php generateCustomData.php