Refactor|Console: Compiling a list of console words with possible values

This output is for the command line autocompletion.

Refactored the old console routines to allow producing styled text
output out of console objects.
Documentation|Fixed|libdeng2: Apidoc issue in Time
libshell|AbstractLineEditor: Added notifications about autocompletion
Client|UI|LineEditWidget: Querying the editor cursor position

Determining where exactly the cursor is on the canvas.
Cleanup
Client|UI|ConsoleCommandWidget: Working on autocompletion popup

Doesn't quite work yet… As popup content, DocumentWidget isn't
visible. What gives?
libshell|AbstractLineEditor: Autocompletion notifications are optional

Derived classes may choose to ignore autocompletion notifications
entirely.
Fixed|libgui|GLBuffer: Buffer not ready with an empty buffer

If an empty buffer is defined, it is still valid for drawing. A buffer
needs to be cleared (released) to really be a "not ready" asset.
Fixed|libdeng2|RuleRectangle: Rule invalidation issue

Related outputs of a rule rectangle (e.g., top affects height & bottom)
need to be invalidated regardless of whether the output itself already
is invalid.

Fixes a problem where accessing only a certain output of a rule
rectangle wouldn't cause the relevant value updates to occur
(DocumentWidget inside a popup).
libgui|libdeng2|Client: Added a way to reset indent in rich format

In the rich format, the indent reset is inserted as an empty range,
so that it can be applied as the last thing on a line. If it were
included in the range that includes a newline, FontLineWrapping would
skip it as it only operates on whatever is between newlines.

The escape sequence for reseting indent is '<'.

EscapeParser was adjusted accordingly (< was previously thought to
begin a long sequence terminated by >).
Refactor|Console: Searching for known words that match the pattern exactly

AFAICS, there is no other way to locate a particular known word.
Client|UI|Default Style: Console command line autocompletion popup

A DocumentWidget is used to display all the possible completions in
a popup.

Todo: Make it a background task to wrap the document text initially,
as it may take a while with longer lists.
Merge branch 'master' into shadow-bias-c++