Don't erroneously preserve backslashes when parsing CoqProject files
Added _CoqProject support to the CoqProjectImpl class

CoqProjectImpl can now -- optionally -- read its load path configuration
from the _CoqProject file. Editing this file doesn't yet cause CoqBuilder
to be triggered, however
Increased the coqtop buffer size "slightly"

The coqtop buffer size is now 32K (five hundred and twelve times larger).
This change has two practical upshots: shorter goals can now be read
instantaneously, and longer goals don't freeze Kopitiam
Convert coqtop end-of-stream errors into normal CoqTypes.Fail results

This stops the code from failing with a mysterious NullPointerException if
the underlying coqtop instance goes away
Replaced the Coq restarting action with a Coq stopping action

The Coq editor starts Coq on demand, so an explicit restart action is
unnecessary. (This is a more useful action anyway, as it gives Windows
users a way of stopping an out-of-control coqtop process!)
Don't create error markers if the underlying coqtop process was stopped