Add generate_days script

- Add generate_days script to generate templated files for an advent of
  code year.
- Optimize the fetch.sh script (remove awk usage)

generate_days.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+leading_zero() {
+    printf '%02d\n' $1
+}
+
+if [ $# -le 1 ]; then
+    echo "year and amount of days arguments not passed"
+    exit 1
+fi
+
+mkdir 'src/'$1
+mkdir 'res/'$1
+for i in $(seq 1 $2); do
+    i2=$(leading_zero $i)
+    cat Template.cpp |
+        sed 's/$1/'$1'/g' |
+        sed 's/$2/'$i2'/g' > \
+            'src/'$1'/Day'$i2'.cpp'
+    res_dir='res/'$1'/day'$i2'/'
+    mkdir $res_dir
+    touch $res_dir'/test_input.txt'
+done