Implement EZP-23772: Support for using custom http cache & class loader

Closes #53

Based on work by @patrickallaert, but adapted for the comments in #53 to
support custom class loader, and also added in the new apache/nginx vhost doc.
EZP-23772: Minor grammar fixes
Merge pull request #202 from ezsystems/custom_cache_n_classloader_env

EZP-23772: Support custom http cache & class loader