feature(file): display file upload limit on file upload form

Refs #6355
feature(groups): Added featured groups as a tab along with groups, popular, discussions

Slightly changed and combined work of @thuvalpakshi
fix(embed): embed jquery target is now searched for instead of assuming last class
Merge pull request #6796 from beck24/embed_js

fix(embed): embed jquery target is now searched for instead of assuming last class
Merge pull request #6876 from Elgg/1.9

Merge 1.9 to 1.x
Merge pull request #6930 from Elgg/1.9

Merge 1.9 up to 1.x
chore(docs): Point INSTALL.txt to learn.elgg.org

Don't want to have to keep these two versions of instructions in sync.
feature(requirements): PHP 5.3.3+ is now required

Symfony needs 5.3.3 and we plan on using their components heavily.

Closes #6165
Merge pull request #6926 from ewinslow/php-53-b6165

Require PHP 5.3.3+ to run Elgg
perf(session): speed up elgg_is_admin_user()

This function currently makes one query and generally hits the query cache
several more times. This generally eliminates the query and avoids the overhead
of the DB service. If a query must be done we use a minimal result set.
Merge pull request #6947 from mrclay/is_admin_user

perf(session): speed up elgg_is_admin_user()
Merge branch '1.9' of http://github.com/Elgg/Elgg into 1.x

Conflicts:
	composer.json
Merge pull request #6972 from THINKGlobalSchool/display-file-upload-limit

feature(file): display file upload limit on file upload form
Merge pull request #7029 from Elgg/1.9

Merge 1.9 up to 1.x
fix(config): path is derived from PHP, not database

Elgg falls apart if `$CONFIG->path` is set to anything but the Elgg root,
so there is no point in saving a different value to the DB
or in respecting any value already saved to the DB.

Refs #2316
chore(composer): add more detailed requirements to composer.json
chore(composer): Ran composer update
Merge pull request #7068 from ewinslow/composer

chore(composer): add more detailed requirements to composer.json
Merge pull request #7069 from ewinslow/config-b2316

fix(config): path is derived from PHP, not database
chore(composer): Rely on composer autoloader to load core classes