Tab state overrides by class or HTML5 history state

Necessary to switch from tree view to list view programmatically,
which reloads the whole tabset and needs to enable the "list" tab.
Used for the new "Show list as children" functionality in the cms.
FIX SplFixedArray causes segfaults in old versions of PHP
Merge pull request #1297 from silverstripe-rebelalliance/feature/config

FIX SplFixedArray causes segfaults in old versions of PHP
Merge pull request #1288 from chillu/pulls/tab-state-overrides

Tab state overrides
Docs - Howto: Customize the Pages List in the CMS
Merge pull request #1291 from chillu/pulls/update-pages-list

Docs - Howto: Customize the Pages List in the CMS
Updated browser requirements, dropping IE7 support

See https://groups.google.com/forum/?fromgroups=#!topic/silverstripe-dev/GahZfDLvb-I