UI updates and other improvements

Changed the UI to allow for searching of users, while still retaining
old functionality.  Added confirmation table so the user using the
plugin can see the users they are merging, as well as final warning.
Also updated database supported functionality as not all MySQL database
engines support transactions.  Finally added configuration option to
make it optional to suspend the user.
adding support for complex quiz attempt structure

Quiz attempts are another complex compound index.  When both users
merging have attempted the same quiz, instead of deleting the old one’s
records we want to preserve the data.

This update also adds in the ability to add custom processing for any
compoundIndex instead of just deleting the old user’s data.
changes related to jordi's comments

Updates and code refinements based upon Jordi’s suggestions
fixing code issues

Forgot to change these to “||” :)  This should do it
moodle-tool_mergeusers - WIP: revisiting contribution code

    * Removed unnecessary translation strings. Replaced by Moodle core strings.
    * Translated strings to Catalan and Spanish.
    * Add a new settings option to enable merging only when transactions are allowed (but not used yet).
    * Moved the "Save selection" button at the bottom of the box for conformance among Moodle specifications.
moodle-tool_mergeusers - WIP: remove description box, since it appears as a help icon in the form.
moodle-tool_mergeusers - #39 : review new UI

Related to issue #39:

* Revisited renderer to add control on radio buttons
  to prevent the same user is selected to both from source
  and target user.
moodle-tool_mergeusers - #39 : revisited renderer

Related to issue #39.

* Build a new renderer method to only build the HTML related to
  the user presentation.
* Updated renderer to show user in this way.
* Solved a visualization bug when target user does not exist.
* Formated files.
moodle-tool_mergeusers - #39 : user ordering

Related to issue #39:

* List of matching users appears ordered by lastname, firstname.
moodle-tool_mergeusers - #39 - search UI

Related to issue #39.

* New UI for searching and confirming users to merge.
* Progress bar added.

All based on John Hoopes contribution.
moodle-tool_mergeusers - #39 : bug solved

Related to issue #39.

* When doble clicking to the same radiobutton, the sibling radio button
  was reenabled, when it shouldn't.
moodle-tool_mergeusers - #39 : discarded quizzes

Related to issue #39.

* This issue is only related to the new UI with search
  and confirmation capabilities, and also with progress bar.
* Therefore, contribution to process quizzes on merging is
  discarded from this issue to be removed to issue #19.

Thanks John Hoopes for all your effort.
Merge branch 'issue39' of https://github.com/jpahullo/moodle-tool_mergeusers into jpahullo-issue39
Merge branch 'jpahullo-issue39', cf. https://github.com/ndunand/moodle-tool_mergeusers/pull/44