raspi: Disabled unless explicitly enabled by user

Add a raspi enabled stanza to lcd4linux.conf file to enable:

Plugin raspi {
    enabled 1
}

Signed-off-by: Jonathan McCrohan <jmccrohan@gmail.com>

git-svn-id: https://ssl.bulix.org/svn/lcd4linux/trunk@1197 3ae390bd-cb1e-0410-b409-cd5a39f66f1f