profiles: add missing APACHE2_MODULES flag descriptions.

profiles: add missing APACHE2_MODULES flag descriptions.

Apache 2.4 adds some new modules whose descriptions are missing from
profiles/desc/apache2_modules.desc. Add the new descriptions, and fix
the order of two existing flags.

Descriptions are added for,

  * authn_core
  * authz_core
  * cache_disk
  * lbmethod_bybusyness
  * lbmethod_byrequests
  * lbmethod_bytraffic
  * lbmethod_heartbeat
  * proxy_fcgi
  * proxy_wstunnel
  * ratelimit
  * remoteip
  * slotmem_shm
  * socache_shmcb
  * unixd

The flags "charset_lite" and "rewrite" are placed in alphabetical order.

Gentoo-Bug: 478540