Add buildIncludeRegexString() stub function

As an initial step in implementing the JLine::isInclude() function, a
regex is needed to match against Java "import" statements.

The pproach used when detecting method headers will be used here as well:
that is, to use a function that builds the regex piece by piece (for
better documentation).

This function made to build the include regex string is
JLine::buildIncludeRegexString().
Impl buildIncludeRegexString function

The JLine::buildIncludeRegexString function was implemented in this commit.

The function documents the creation of a regex string, piece by piece.  The
import string is much simpler than the previous regex used (for finding
methods), though it has been through a little less testing so far.
Impl JLine::isInclude()

Simple regex check using buildIncludeRegexString() and checkRegexMatch
was used to implement isInclude()