Add plugin support for ignorelists
KDiff3 currently only supports cvsignore files. This was fine when it was first created however cvs is non-longer the dominant player it once was. This problem of bit rot is inherent to any design that attempts to hardwire such support in the main program. Ignore file support should be an extensible plugin feature. Some formats can and perhaps should be included by default but one should not need to rebuild kdiff3 to get addition support.