This commit moves all the logic that deals with the language server
(from HackStudio) into a LanguageClient class, provides some functions
to make constructing them easier, and makes all language servers use a
singular IPC definition.
Also fixes the FIXME about making the autocompletion async.
This makes adding language servers in the future significantly less
duplicate-y, and significantly easier :^)
The language server keeps track of the content of currently edited
files by receiving updates about edit actions.
Also, C++ autocompletion is no longer tied to HackStudio itself and
moved to be part of the language server.
CppAutoComplete gets a string of code and a position within it, and
returns a Vector of auto-complete suggestions that are relevant for the
given position.
Currently, it's very naive - it uses our CppLexer to find identifiers
in the code which the auto-complete target is a prefix of.
This commit adds a new GUI widget type, called CodeDocument, which
is a TextDocument that can additionaly store data related to the
debugger.
This fixes various bugs and crashes that occured when we switched
between files in debug mode, because we previously held stale breakpoint
data for the previous file in the Editor object.
We now keep this data at the "document" level rather than the Editor
level, which fixes things.
