Migrate the clients.config and jetty.xml files
from Jetty 5/6 to Jetty 7/8.
Also migrate jetty.xml from Jetty 7/8 to Jetty 9.
For each client for class org.mortbay.jetty.Server:
Let $D be the dir that jetty.xml is in (usually ~/.i2p/eepsite)
Saves $D/jetty.xml to $D/jetty6.xml
Copies $I2P/eepsite-jetty7/jetty.xml to $D/jetty.xml, edited for $D
Copies $I2P/eepsite-jetty7/jetty-ssl.xml to $D/jetty-ssl.xml, edited for $D
Copies $I2P/eepsite-jetty7/jetty-rewrite.xml to $D/jetty-rewrite.xml
Copies $I2P/eepsite-jetty7/context/base-context.xml to $D/jetty.xml, edited for $D
Copies $I2P/eepsite-jetty7/context/cgi-context.xml to $D/jetty.xml, edited for $D
Copies $I2P/eepsite-jetty7/etc/* to $D/etc
Changes main class in clients.config
Copies clients.config to clients.config.jetty6;
Saves new clients.config.
Does NOT preserve port number, thread counts, etc. in the migration to 7/8.
DOES preserve everything in the migration to 9.