Remove deprecated function add_contextual_help

[Mamaduka]

With WordPress 3.3 add_contextual_help() function is deprecated, need to update them with new add_help_tab() function.

Here's dev note from Nacin about ​Help and screen API changes in 3.3

[Mamaduka]

Working on a patch, but add_help_tabs is little tricky to use with CPT and how bbPress added contextual help before. One problem is that calling setup_help() in construct is early for WP_Screen, I attached setup_help() function to load-$pagenow hook but it needs extra logic like - is it forum post type, is it edit or add screen.

[johnjamesjacoby]

(In [3685]) Refactor bbp_admin_settings_help() to use add_help_tab() and set_help_sidebar(). See #1699.

[johnjamesjacoby]

(In [3686]) Refactor forum/topic/reply contextual help, shamelessly sampled from the WordPress 'post' content type. See #1699.

[johnjamesjacoby]

(In [3687]) Hook missing forum contextual help in. See #1699.

[johnjamesjacoby]

Closing this as fixed,as the bulk of the code changes are in. Would love if someone would comb through the verbiage and check for feature pairity since it's largely lifted from WordPress core.

[Mamaduka]

Previous changes to contextual help where missing forum/topic/reply Attributes box help tabs, also I believe there are no pages in Codex for forum/topic/reply Formats, so for now links will redirect users to Post Format page.

[johnjamesjacoby]

(In [3688]) Add attributes to forum/topic/reply contextual help. Props Mamaduka. Fixes #1699.

[johnjamesjacoby]

(In [3718]) Add description to Group Forums Parent setting. Remove check for forums not being active, as this will be handled by migration later. See #1699.