fix(discussion): discussion replies respect previous subscribers

Existing subscribers to discussions were ignored when getting the
interested users for a discussion reply.

fixes #7281
fix(css): prevent select box from overflowing its container

Fixes #7290
docs(plugins): Information on activation/deactivation

Copied information on activate.php and deactivate.php from legacy documentation and linked to
older information on plugin skeleton.
Merge pull request #7293 from stianlik/patch-2

Adds information on plugin activation/deactivation
Merge pull request #7291 from PerJensen/fix_select_overflow

fix(css): prevent select box from overflowing its container
fix(database): More robust sql script execution.

Implemented tests for various formats of SQL input and fixed a bug that caused
text inside SQL strings to be interpreted as comments. Specifically, "INSERT
INTO x values ('some string -- not a comment');" is now supported. Also added
support for comments prefixed with "# ".
chore(views): removed unused group link code in river summary view
chore(likes): removes warning about undefined delete_button variable
Merge pull request #7297 from jdalsem/unused-code-river-summary

chore(views): removed unused group link code in river summary view
fix(aalborg_theme): display search when logged out

Referencing #7169
docs(web_services): Documentation for Elgg 1.9

Updated function names to be compatible with Elgg 1.9. Information about
migration from 1.8 to 1.9.
Merge pull request #7292 from stianlik/patch-1

Documentation for Elgg 1.9
Merge pull request #7298 from juho-jaakkola/likes_undefined_delete_button

chore(likes): removes warning about undefined delete_button variable
Merge pull request #7294 from stianlik/1.9

fix(database): More robust sql script execution.
Merge pull request #7301 from PerJensen/search_fix

fix(aalborg_theme): display search when logged out
Merge pull request #7282 from jeabakker/discussion_subscriptions

fix(discussion): discussion replies respect previous subscribers