Add max-commit-count parameter to cgitrc

This enabled customizing number of commits shown per page in log view. It
also changes the default from 100 to 50, mainly due to the more cpu
intensive log pages (number of files/lines changed) but also since 100
log messages requires excessive scrolling.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgitrc

@@ -55,6 +55,10 @@
 #max-message-length=60
 
 
+## Number of commits per page in log view
+#max-commit-count=50
+
+
 ## Root of cached output
 #cache-root=/var/cache/cgit