To replace configuration files that have been deleted, without purging the package, you can do
sudo apt-get -o DPkg::Options::="--force-confmiss" --reinstall install apache2.2-common
To fully remove the apache2 config files, you should
sudo apt-get purge apache2.2-common
which will then let you reinstall it in the usual way with
sudo apt-get install apache2
Purge is required to remove all the config files - if you delete the config files but only remove the package, then this is remembered & missing config files are not reinstalled by default.