www/tomcat[6|7|8]: Bring improvements from Tomcat[85|9]

- Add options [1]
  Based on Apache Tomcat documentation guidance, the default web applications
  have varying degrees of risk, these options will permit users to select
  which of the web applications should be installed.

- Remove start_precmd from rcfile in Tomcat7 and Tomcat8 [2]
  This is not being used, users can use ${name}_env to pass variables

- Mark additional config files as @sample [3]

PR:		218865 [1]
PR:		228418 [2]
PR:		229102 [3]

Submitted by:	Matt <fsbruva@yahoo.com> [1]
Submitted by:	VVD <vvd@unislabs.com> [2] [3]
Reported by:	Michael Osipov <1983-01-06@gmx.net> [2] [3]
Approved by:	ale ???
Differential Revision:	https://reviews.freebsd.org/D16499