GROOVY-6389: groovysh: Print results using toString(), not String.valueOf

Using java.lang.String.valueOf(obj) for instances of Arrays and Maps causes
Object.toString to be used for String generation, causing ugly output in groovysh

This commit uses toString() instead which uses pretty output for collections.

As opposed to an earlier commit for Groovy 2.2, Arrays will be displayed
without their type. Avoiding the GString here because of the earlier code
comment, not sure whether there is any risk using GString here or not
(Comment was from 2007, e222d4f5cf8cc7).
replace other occurences of String.valueOf in groovysh
GROOVY-6391: groovysh: fix bad member name
Fix invalid AnsiDetector after migration to jline2
make test succeed even if ANSI is not supported by test platform
removed unnecessary imports
Merge pull request #270 from tkruse/style_fixes
groovysh: fix bad method name createCompleto/ers
Documentation Fix for ConfigSlurper
GROOVY-6385: groovy.bat: Can't use question mark in script parameters

As suggested by Dominique on the mailing list:

http://groovy.329449.n5.nabble.com/Can-t-use-question-mark-in-script-parameters-td5716658.html
GROOVY-6118: @Mixin annotation is not visible in runtime
GROOVY-6401: Method return type inference breaks with inheritance