new CLI argument: provide abililty to show debug level of logs from checkstyle code

[romani]

base on discussion at #3085 and a lot of other cases that were before.

We should have some way to "trace" what is going on in Checkstyle by directing logs to output.
New CLI argument need to be created "-d" "--debug" to show DEBUG level of logs.
All logging in Checkstyle should be done on with DEBUG and TRACE level. INFO and WARN and ERROR already user for severity so lets not mix them.

for now we use apache logging (example), dependency is transitive:

$ mvn dependency:tree | grep -B 4 logging
[INFO] com.puppycrawl.tools:checkstyle:jar:6.18-SNAPSHOT
[INFO] +- antlr:antlr:jar:2.7.7:compile
[INFO] +- org.antlr:antlr4-runtime:jar:4.5.3:compile
[INFO] +- commons-beanutils:commons-beanutils:jar:1.9.2:compile
[INFO] |  +- commons-logging:commons-logging:jar:1.1.1:compile

I personally fan of slf4j logging api usage. But switching to slf4j will mean extra dependency to our library. For now we have almost no logging. So for now lets stay with apache common logging till amount of logs become significant and verbose format

if (log.isDebugEnabled()) {
 log.debug(".....")
}

is bearable. But all log usages should be wrapped for now, as we are a library.

[romani]

fix is merged.