feature(views) Eases extending the input/view view

In order to extend forms *outside* the form element, devs must extend the 
input/form view, however it's a bit cumbersome to determine the current
action because you have to extract it from the "action", which is a URL. This
gives the extending view the raw action name.

Fixes #6129
security(http): Adds anti-clickjacking header when serving pages

Adds a header that prevents framing pages from different domains in
modern browsers. A plugin hook allows disabling/altering the headers
sent.

Fixes #6098
fix(embed): make tabs in colorbox popup usable

Function embed_select_tab expects input page to be set, but it isn't.
Adding a
´´´
set_input('page', $page[1]);
´´´
to the embed_page_handler function fixes this

Refs: Issue #6357
Merge pull request #6348 from mrclay/6129

Eases extending the input/view view
docs(hooks): Corrects docs syntax error
Merge pull request #6380 from Srokap/pr/6331
feature(output): Added second parameter to elgg_strip_tags.
Merge pull request #6324
fix(views): Correct default title for confirmlink

Wrong key was used from $vars when 'title' was not passed.
It now correctly defaults to 'confirm'.

Closes #6375
Merge pull request #6376 from hellekin/fix-6375

Fix wrong key from $vars (closes #6375)
Merge pull request #3 from mrclay/sembrestels-embed-editing-comment

fix(lightbox): Correctly applies color box options on each element
fix(groups): displays correct group content access options for each content access mode

Content access options for public groups:
 - Private
 - Logged in users
 - Public
 - Members of the group

Content access options for groups using members-only policy:
 - Private
 - Members of the group

Refs #6142
feature(graphics): make logos transparent

Adds transparency to branding

#6398
Merge pull request #6399 from hypeJunction/logos

Fixes #6398: make logos transparent
Merge pull request #6384 from mrclay/slyhne-patch-7

Fixes pagination and group file finding in embed
Merge pull request #6378 from sembrestels/embed-editing-comment

fix(lightbox): lightbox wasn't shown when generated from ajax view.
Merge pull request #6393 from juho-jaakkola/group_access_settings

Display correct access options for group content
Merge pull request #6363 from slyhne/patch-6

fix(embed): make tabs in colorbox popup usable
feature(events): allows passing $params variable to event handlers

Plugin hooks allow the trigger to pass useful contextual information to handler
functions. This gives event triggers the same ability.

Fixes #6035