Update defaults on new parts in the New Part tool

This patch makes all new parts of all types have
reasonable default sizes, whereas before only new
normal parts were resized to (4, 1, 2).

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Update README.md (include info about groups, shortcuts)

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Update README.md (build and contributing info)

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Stop multiselection upon releasing left mouse button

This patch fixes a bug where multiselection does not stop if
the left mouse button is released atop a core GUI.
Fix the way the plugins check if Studio is in solo mode

Previously, they checked for the existence of a Visit instance
under Game, but that instance is also added when opening the place
from green Edit buttons, such that it's not a reliable way of
knowing when it's in Solo or not. There's no official way to
check this, so waiting a while for players may be the best,
most accurate way to go for the moment.

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Fix 2D selection session cutoff

Another bug plaguing the 2D selection system
didn't let it know when the mouse was actually
being released. This has been fixed by using
UserInputService to tell when the mouse is
actually released, instead of the Mouse object.

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Fix the cutoff when dragging with the move tool

Dragging sometimes continued after letting go of
the left mouse button if that happened to be over
a tool button on the dock UI. This has been fixed
by cleaning up the dragger when unequipping the
tool.

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Improve contrast between the groups UI and light backgrounds

This patch introduces a better group ignore icon
and a darker group button.

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Make newly created groups contain selected items

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Add labels to the buttons in the groups UI

Signed-off-by: Robert Chiquini <gigsd4x@gmail.com>
Merge branch 'development'