This commit introduces support to the LTI module for LTI 2.0.
As well as the initial commit the following changes were made
and then squashed into the single commit for integration:

* Fixed bug in services
  Fixed bug which limited characters allowed in values of template
  variables (e.g. vendor ID) in service endpoints.
  Changed language file to refer to tool registrations rather than
  tool proxies.

* Refactored service classes
  Moved classes relating to services into areas where Moodle will
  autoload them

* Ran code through code checker
  Removed all errors reported by the Code checker module
  excluding third-party OAuth.php file.

* UI improvements
  Mainly when adding an external tool to a course - fields which
  should not be changed for a selected tool are either hidden or
  disabled. Admin settings page now shows the Tool Registration
  name against a tool rather than the launch URL, and the
  registration URL replaces the GUID on the tool registrations
  page.

* Updated tool proxy registration
  Added check of tool proxy to ensure only offered capabilities
  and services are included.  Also check tool proxy when processing
  a service request.

* Code review changes
  Some fixes based on code review by Mark Nielsen and addition of
  some PHPDocs comments.

* Updates from code/PHPdocs checks
  Removed use of eval and corrected invalid PHPdocs for new
  functions/classes

* Corrected namespace error and incorrect string terminator

* Updates based on forum feedback
  Added dependencies and backup, restore and uninstall methods for
  ltiservice subplugins.
  Changed most uses of is_null to empty

* Updated custom parameters test
  Updated test_split_custom_parameters to include new function
  parameters.
  Corrected PHPdoc entry for lti_split_custom_parameters
  Fixed incorrect line separators in ltiservice.php

* Added require_capability to registrationreturn.php

* SQL and EOL updates
  Moved PHP variable in SQL into a named parameter
  Improved checks for end-of-line characters to include CR and LF
  on their own or together

* Check for semicolon separators
  Semicolon separators in custom parameters are changed to EOL
  characters when upgrading to the 2014100100 version.

* Remove unused file
  basiclti.js file not being used so removed.

* Adjust line lengths
  Split long lines in upgrade.php

* Added savepoint to upgrade.php
  savepoint omitted from earlier update to upgrade.php

* Updated namespaces and upgrade
  Service and resource classes moved into .../local/...
  Upgrade SQL moved into a function and unit test created

* Updated lti_tool_proxies table
  Added indices and foreign keys to lti_tool_proxies table

* Fixed formatting and documentation issues

* ltiservice class moved into local

* Replaced lti_scale_used comments
  Put back commented out code for lti_scale_used

* Removed redundant sesskey code

* Fixed namespace and path check
  Updated ltiservice namespace for move into local
  Added check for existence of $_SERVER['PATH_INFO']

* Updated upgrade code
  Added indices and keys to lti_tool_settings table when upgrading
  Fixed errors in upgradelib_test.php (thanks to jleyva)
  Update SQL to use Moodle functions

* Use of empty with class method
  PHP 5.4 does not like the use of empty with a class method so saved the
  value to a variable first.  PHP 5.5 seems to accept the use of a method
  with empty.

* Removed redundant indices
  Removed creation of indices for foreign keys on lti_tool_settings table
  from install.xml and upgrade.php

* Fixes based on feedback
  Minor changes and corrections based on review in JIRA

* Fixed bug in toolproxy service
  Corrected bug which failed to respond properly to an invalid request
  Also updated upgrade.txt file

* Improved admin navigation
  Added the manage tool registrations page as a separate entry on the
  admin menu (within a folder named LTI).  Made this entry the current
  position for the related pages.

* Updated PHPdocs with class names
  Added class names with namespaces to PHPdocs to replace generic
  references to "object"

* Changed object to iframe
  Use of object tag in register.php changed to use an iframe tag in line
  with the similar update made to view.php.

* Improved registration process
  A message is now displayed if the registration page has not been loaded
  in the iframe within 20 seconds.  If a user is returned to Moodle
  without a tool proxy being sent, the registration is moved back from
  pending to configured.

* Fixes for integration
  Removed comment - the template is the default path unless overridden, so
  get_path and get_template should both be defined.
  Added comment and intval to fix the issue with obtaining an error
  reason.