Bug 10480: New module and unit test for framework plugins

Bug 10480: New module and unit test for framework plugins

This patch introduces the Koha::FrameworkPlugin object to Koha.
This object supports the current "old-style" plugins while adding a new
style based on the concept of two anynomous subroutines for building and
launching.

I will summarize the advantages of this new approach, justifying the
additional lines of code in this patch:

[1] Centralizing the code for building and launching plugins.
[2] Extensive unit testing: this was not possible before.
[3] Simplicity: Only define what you need in the plugin.
    A follow-up patch will delete 1500 lines with *empty* routines.
[4] Make it possible to restore the warnings pragma for all plugins.
    New style plugins do no longer depend on redefinition.
[5] Event binding moved from HTML attributes moved to jQuery code.
    This separates behavior and presentation.
[6] Much more documentation, including EXAMPLE plugin in follow-up.
[7] Improved error handling.
[8] Usability: property noclick tells you if plugin's buttonDot is active.
[9] More events supported: Change, keyboard/mouse events. See EXAMPLE.

NOTE ON EXAMPLE PLUGIN:
The example plugin is added in the third patch of this report. Since
it is new style, it can be used only after we start using this object. It
also contains an example for a keypress and mouseover event.

NOTE ON ITEM PLUGINS:
Old style plugins for items contain an additional parameter in the js
functions for Blur, Focus and Change. This distinction has no actual use
and is resolved for new plugins in the object code. When converting
item plugins, this minor correction will be addressed. In the meantime
old style item plugins behave as expected.

TEST PLAN:
Run the new test t/db_dependent/FrameworkPlugin.t
At this point in time, you do not need to do anything more. Follow-up
patches will incorporate the object in real-life Koha and provide
additional test plans.

Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>