Blender Git Loki

UI: Add tooltips for modifiers

When adding a modifier to an object, the drop-down select box has the
same mouse-over tooltip for each modifier type: "Add a procedural
operation/effect to the active object". This isn't helpful when you
don't know what the modifier does from just reading the name.

This patch adds descriptions for most modifier types, so that it's
clearer what the modifiers do. The text was provided by @werwack after
discussion on DevTalk[1] and taken from the Blender Manual, and
subsequently updated by @billreynish and @HooglyBoogly.

Not all modifiers have a short one-line description in the manual, hence
those are still missing in this patch.

[1] https://devtalk.blender.org/t/ui-contextual-modifier-description-in-the-tooltips-of-the-add-modifier-dialog-window/10382

Reviewed By: billreynish

Differential Revision: https://developer.blender.org/D6352