*9037* Show titles in TOC as configured in manager/languages

A very few modifications in core to get more control about how language is shown in TOC in multilang journals.
The aim of the modifications was commented here:
http://pkp.sfu.ca/support/forum/viewtopic.php?f=9&t=13021&p=49967
The new feature also requires modifications submitted to "lib-pkp" submodule.

A deep review of the code (and specially of the literals in locale/en_US/manager.xml) is encouraged.
The getLocaleDisplayTitle functions don't appear to be used anywhere. Did something get left out of the PR?
Also, are these ever going to be called outside of the journal context? If not, then we can remove the additional complexity (e.g. the DEFAULT_LOCALE_DISPLAY constant).