use comment form customization function also for the comment form in the page area

issue #17
added and implemented option to remove email field

issue #9
added and implemented option to remove website url field in guestbook comment form

issue #9
added option to change comment field label in guestbook comment forms

changed filter priorities
issue #9
fixed comment
updated comment_form section description (for comment form modifications in page/post)
updated screenshot 3
preparation for version 0.6.2
Merge branch 'develop'