Several tweaks in the Windows scripts

Previously, to install KA Lite in windows using the .bat scripts there was a need to add python in path and also there was no control over the cronserver process. The stop.bat script would stop ALL python processes which in many cases, may be annoying to the user.

- I have changed all the scripts to use the "start" command which is used as a proxy to python, eliminating the need to add it to the path. 
- Both install.bat and start.bat, will now check if python is installed and if not, they will inform the user.
- The stop.bat will now stop the cron and cherryPi instead of all python processes running.

Edited files:
- install.bat
- start.bat
- cronstart.bat
- serverstart.bat
- stop.bat