Remove method-regex code from JCodeFile

Recent design decisions placed the burden of analyzing single lines of code
in the hands of the Line and JLine classes.

In accordance with this design, this commit removes code that attempts to
search a file for method headers from JCodeFile.  An upcoming commit shows
this code reappearing in JLine
Implement JLine::isMethod() method.

To implement the JLine::isMethod() function, existing code was refactored
from JCodeFile.  This code was inserted into the isMethod() function.

In addition to filling the body of the isMethod method, the method
buildMethodRegexString was moved into the JLine function, and removed
from JCodeFile.  This method is responsible for documenting the regex
used to identify Java method headers.