[ticket/11445] Optimize no of queries in get_global_subscriptions

PHPBB3-11445
[ticket/11445] Improve unit tests for get_global_subscriptions

PHPBB3-11445
[ticket/11445] Remove unused foreach key $group_name

PHPBB3-11445
[ticket/11445] Move get user's notification code into its own method

PHPBB3-11445
[ticket/12682] Make Code Sniffer run properly on Travis CI again.

The --ignore parameter takes a case-insensitive pattern and as such
'phpBB/phpbb/*' matches any '/home/travis/build/phpbb/phpbb/...' file name.
This results in nothing being checked against ruleset-php-legacy.xml.

Using absolute paths in the --ignore pattern fixes this issues.

PHPBB3-12682
Merge pull request #2582 from bantu/ticket/12682

[ticket/12682] Make Code Sniffer run properly on Travis CI again.

* bantu/ticket/12682:
  [ticket/12682] Make Code Sniffer run properly on Travis CI again.
Merge pull request #2527 from dhruvgoel92/ticket/11445

[ticket/11445] optimize no of queries in get_global_subscriptions( )

* dhruvgoel92/ticket/11445:
  [ticket/11445] Move get user's notification code into its own method
  [ticket/11445] Remove unused foreach key $group_name
  [ticket/11445] Improve unit tests for get_global_subscriptions
  [ticket/11445] Optimize no of queries in get_global_subscriptions