cleaned up the MySQL maintenance section a bit

Signed-off-by: Joerg Steffens <joerg.steffens@dass-it.de>
mention the innodb_file_per_table bit

Signed-off-by: Joerg Steffens <joerg.steffens@dass-it.de>
mention InnoDB and clean up mysql repair section

Signed-off-by: Joerg Steffens <joerg.steffens@dass-it.de>
adapt some formating