- task: rename some functions to avoid namespace conflicts in addon modules

- bugfix: report version info for all gallery* modules
- bugfix: session handling to prevent TempIds
- bugfix: session handling to workaround [sf#1967484] new admin session protection (#250770)
- bugfix: hide search for user without proper permission
- feature: integration with advanced help module (TODO: write documentation)
- task: cleanup block tpl code
- task: add base api version constant

- bugfix: block cache per user for navigation (#227888)
- task: make imageblock settings reusable

- bugfix: gallery_menu admin fails if no gallery block is enabled

(requires G2.3/svn and is still volatile, for early testing only)

It's almost all or nothing. Without access the user cannot see the gallery
or gallery blocks. However, embedded thumbnail images in nodes are still
visible (but the link won't work).
You also need to set 'mode.embed.only' to true in your Gallery2 config.php
file to avoid bypass via standalone.

IMPORTANT: You will need to set the user permissions to 'access gallery'
for the roles you want to be able to see the gallery.

Split gallery_block into separate .inc file.
Added configuration of g2Image file types.
#57894 - Fixed theme specific css file import.