Made BaseCoqEditor actually create Coq source viewer configurations

Commit 90d7c02a4302af8f5cabd0527219a0a20d8c2960 was actually supposed to
include this functionality. Oh, well: better late than never
Added a plugin wrapper for a snapshot of PIDE with Coq support

The Coqoon UI plugin is about to acquire a dependency on this plugin, and
the Coqoon core will eventually do so as well
All plugins and features should use the Scala 2.11 library identifier
Added a dependency upon PIDE to the Coqoon UI plugin

This commit also adds the PIDE plugin to the Coqoon feature
Added a blue-tinted variant of the Coq document icon

A second editor for .v files, which will use PIDE to communicate with Coq,
is about to be added; this slightly different icon will make it possible to
tell which interaction mode is being used
Added the text of the licence of Isabelle to the Coqoon feature licence

This is also included in the PIDE plugin, but it's good to be thorough
Added a new Coq editor that uses PIDE for Coq interaction

This editor is incomplete and dangerously experimental, but it's a start!
Once support for error markers and the goal viewer has been implemented,
it'll be ready for release as a technology preview
Registered the new PIDE Coq editor as an alternative editor for Coq files
Split the CoqTopContainer trait into several more basic traits

The PIDE Coq editor will need to have goals associated with it, but it
definitely won't have an instance of coqtop -ideslave! These new traits
will allow objects to expose goals without needing such an instance
Made the GoalViewer class check for the CoqGoalsContainer trait

As this change removes the only code that referenced the deprecated
CoqTopContainer.PROPERTY_GOALS constant, this commit also removes that
Added utility methods for extracting PIDE results and markup from commands

The markup gives us metadata about successfully-parsed commands, and the
results tell us when something's gone wrong. That's all we care about for
the moment, at least
Added error marker support to the PIDE Coq editor
Added support for (foreground) goals to the PIDE Coq editor

This looks great and works really well. All that's left to do before the
first preview release is the load path initialisation document fragment
The Coq PIDE editor should respect project load path configurations

This is implemented in a hilariously bad way at the moment: Coqoon smuggles
an invisible region containing Add Rec LoadPath commands into the start of
the document and then lies about message offsets to hide it. On the other
hand, it works, and it should also make it possible to update the load
paths without having to restart Coq
Print PIDE protocol messages when the ideslave debug option is enabled