support for install a package's dependencies
able to resolve nested dependencies properly
add apr package
add apr_util package
add apache2 package
add libmcrypt package
add php5 package
add composer package
refactor apache2 package

- use a layout to install files. Much better default configuration now
- always rewrite etc/apache2/httpd.conf upon install. Customized configuration
  should go into etc/apache2/config/*.conf
fix php5 config

- move libphp5.so out into package so we can copy it as apache modules without
  having to compile it
- setup php config as individual apache config
Replace nus.edu.sg mirrors with other recommended mirrors
Edit descriptions for LAMP stack packages