main/charybdis: fix initscript & localstatedir location

rewrite initscript because it was pointing to the wrong executable, and
the declarative syntax is simpler to understand and maintain

for localstatedir: /var/charybdis didn't make sense, and the directory
was never created on package install, making it impossible to start
charybdis with default config without further intervention. move to
/var/lib/charybdis and actually create that directory for the user

Creds to : opal hart