(OFBIZ-11587)

- common-sending-email: include in email
- datafile: move as a include at the end of entity-engine section
- entity-engine: list of link to OFBiz wiki about entity configuration
- service-engine: a link to OFBiz wiki Service Engine Guide
- webtools: help for main screen
- mini-lang: include a link to OFBiz wiki mini-lang-reference at the
beginning of minilang-to-groovy-manual
           move minilang-to-groovy-manual to Development environment
section
- unit-test: include as Junit test, and use README to list gradle
command available (so add a tag in REAME.adoc)
- base: add a link to OFBiz wiki Configuration Guide, in deployment
section
- SingleSignOn with LDAP: move to plugin LDAP and include in deployment
section

developer-manual is updated with some include lines or with directly a
sentence.