chore(log): Convert `elgg_log` to OO equivalent in all classes
feature(php): Require PHP 5.4+

PHP 5.3 is currently end-of-life and 5.4 will have only ~1 year of security patches
when Elgg 1.10 is scheduled to be released.

Fixes #7090
chore(insight): Fully qualify class names with `use` or leading backslash

In general, missing `use` statements can lead to bugs or at least ambiguity.
Better to fully qualify all classes.

See "Missing use statement should be avoided" on this report:
https://insight.sensiolabs.com/projects/0630ff8f-809b-4409-a718-12f7da91367e/analyses/5
Merge pull request #7475 from ewinslow/php-54

feature(php): Require PHP 5.4+
Merge pull request #7473 from ewinslow/oo-services-logger

chore(log): Convert `elgg_log` to OO equivalent in all classes
chore(i18n): Remove all global i18n functions from classes
Merge pull request #7472 from ewinslow/oo-services-translator

chore(i18n): Remove all global i18n functions from classes
Merge pull request #7477 from ewinslow/missing-use

chore(insight): Fully qualify class names with `use` or leading backslash